20140228

Astronomy current events question: revived Kepler space telescope mission

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Lisa Grossman, "NASA's Revived Exoplanet-Hunter Sees Its First World," February 6, 2014
http://www.newscientist.com/article/dn24857-nasas-revived-exoplanethunter-sees-its-first-world.html
NASA's newly-revived Kepler space telescope overcame its recent __________ problem to successfully detect an exoplanet.
(A) stabilizing mechanism.
(B) software update.
(C) radioactive leak.
(D) meteorite collision.
(E) solar flare interference.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 40 students
(B) : 0 students
(C) : 2 students
(D) : 1 student
(E) : 2 students

Astronomy current events question: magnifying Abel 2744 Y1

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Whitney Clavin, "Looking Back to the Cradle of Our Universe," February 7, 2014
http://www.nasa.gov/jpl/spitzer/galaxy-cluster-abell2744-20140207/
NASA's Spitzer and Hubble space telescopes used __________ to magnify Abell 2744 Y1, the farthest galaxy discovered to date.
(A) a pocket of dark matter.
(B) pinpointing laser beams.
(C) new digital processing software.
(D) an antique slide film projector.
(E) gravity from a nearby galaxy cluster.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 3 students
(B) : 2 students
(C) : 25 students
(D) : 1 student
(E) : 14 students

Physics quiz question: microscope objective lens focal length

Physics 205B Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

The Richter Optica F1 microscope[*] (–40× magnification) has an eyepiece lens with a focal length of +2.5 cm, with a separation distance of 25 cm between the objective and eyepiece. The focal length of the objective lens is:
(A) +0.63 cm.
(B) +1.6 cm.
(C) +5.6 cm.
(D) +100 cm.

[*] microscopeworld.com/p-1735-richter-optica-f1-elementary-microscope.aspx.

Correct answer (highlight to unhide): (C)

The angular magnification M of a microscope is given by:

M = –((LfeN)/(fo·fe),

where the "tube length" (the focal point to focal point distance) L is given as 25 cm, the nominal near point N is 25 cm, and the eyepiece focal length is fe is also given as +2.5 cm. Thus the objective focal length is then:

fo = –((LfeN)/(M·fe) = +5.625 cm,

which to two significant figures is +5.6 cm.

(Response (A) is N/M; response (B) is M/N; and response (D) is M·fe.)

(Sections 30882, 30883
Exam code: quiz02O8Jt
(No results compiled.)

Astronomy current events question: GAIA surveying mission

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Markus Bauer, Giuseppe Sarri, and Timo Prusti, "Gaia Comes Into Focus," February 6, 2014
http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_comes_into_focus
The European Space Agency Gaia space telescope will begin making routine measurements of __________ in the Milky Way.
(A) Earth-like planets.
(B) star positions and motions.
(C) dark matter.
(D) interstellar gas.
(E) cosmic ray sources.

Correct answer: (B)

Student responses
Sections 30678, 30679, 30680
(A) : 11 students
(B) : 29 students
(C) : 1 student
(D) : 3 students
(E) : 1 student

20140227

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02O8Jt



Sections 30882, 30883 results
0- 6 :
7-12 : *** [low = 11]
13-18 : ******
19-24 : ***************** [mean = 22.0 +/- 5.2]
25-30 : ************** [high = 30]

20140226

Online reading assignment: runaway planets, jovian planets, and dwarf planets (oh my!) (SLO campus)

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on runaway planets (Venus and Mars), jovian planets (Jupiter, Saturn, Uranus and Neptune), and the dwarf planets (and the International Astronomy Union classification scheme).

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"I thought that on the presentation, the slide with the 'frustrated' volcanoes was most interesting to me. This was personally interesting to me because I think the example you gave is great, and it helps me understand it a little more. I didn't know that with crust being thin and flexible, that makes it harder for the magma to push through. I would think the thicker the crust, the harder. But then when I look at Mars, thick and 'gooey' that makes more sense how it would be harder to erupt."

"I personally found the presentation preview on the gas giants and ice giants interesting because I honestly didn't know much about the internal heat of the planets. The coffee GIF animation made it easy to understand."

"I thought it was interesting to learn about the criteria for being a planet because I had never know that before and it's actually something I had wondered about. Like why isn't that floating rock in space a planet? Now I know it's because it has to orbit the sun, have control of it's own orbit and be round which I personally don't really think is fair criteria. I also thought it was interesting to learn about the characteristics of Mars and Venus and what the surface looks like. I would like to learn more about that and about what went wrong with their atmospheres and if that could happen to us."

"I thought it was interesting that Venus and Mars are considered run away planets because their greenhouse gas cycle was hindered in some way. It makes me worry about global warming and how it can truly have devastating effects on Earth. I found it a little shocking that greenhouse gases were partly due to the lack of livable environment on Mars and Venus."

"I found the Mars rover time-lapse movie to be actually quite interesting."

"For some reason I thought that only Earth had an atmosphere...after looking through the book I found that I was mistaken. Learning about what gives a planet a certain kind of atmosphere was very interesting."

"I found it really interesting that the core heat and sunlight basically determine the color of the planet. For example, Jupiter being more colorful than Saturn. When I was in elementary school Jupiter was my favorite planter because its colors!"

"I found it interesting how all the planets were formed relatively in similar yet with the smallest differences they formed into completely different planets. I think its crazy how a little change can allow for earth to have life and other planets uninhabitable."

"I enjoyed reading about Pluto! I was unaware of why Pluto had been stripped of its 'planet' title so I was intrigued to learn what a dwarf planet is!"

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Something that I found confusing is the whole greenhouse factor subject. This is personally confusing to me because I can't wrap my head around it. I get the arrows and what you are saying there, however I need a little more explanation on the whole concept which I'm sure we will learn in class!"

"I found how we think Mars to be hospitable is confusing. To me all the things they are mentioning about this planet make it seem like it is inhospitable."

"Not really sure if were suppose to memorize all of the info in the book on the different planets."

"There are many things I find confusing. Honestly I'm going to wait until the lecture to get my questions answered because I find them hard to word right now."

"I just can't really grasp the runaway greenhouse effect. but I will look on it more to try and understand it."

"It was confusing to figure out if these planets had more or less geologic activity than Earth."

Identify the relative amounts of these characteristics for Venus, compared to Earth. (Only correct responses shown.)
Volcanic outgassing, up until now: about the same as Earth [60%]
Heat from the sun: more than Earth [84%]
Amount of atmosphere, today: more than Earth [82%]
Interior core heat, today: about the same as Earth [44%]
Geologic activity, today: less than Earth [69%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Volcanic outgassing, up until now: less than Earth [71%]
Heat from the sun: less than Earth [80%]
Amount of atmosphere, today: less than Earth [98%]
Interior core heat, today: less than Earth [87%]
Geologic activity, today: less than Earth [76%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).  ** [2]
Saturn (most prominent rings).  ***** [5]
Uranus (least active weather patterns).  ************************ [24]
Neptune (farthest from the sun).  ************ [12]
(Unsure/guessing/lost/help!)  ** [2]

I believe Pluto should be a planet.
Strongly disagree.  * [1]
Disagree.  ************ [12]
Neutral.  ***************** [17]
Agree.  *********** [11]
Strongly Agree.  **** [4]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"I don't have a strong opinion on whether Pluto should be a planet or not. I think it is cool that Pluto was the first to be discovered, and that it is so tiny. But after reading about what defines a planet I guess that makes sense on why they took it off the list of planets. The object needs to be large enough to dominate and gravitational clear its orbital region, which Pluto does not meet the standard."

"It was before--why not now?"

"Before reading this section in the book on Pluto, I would have said that there was no reason to take away Pluto's status as a planet. We had considered it a planet for long enough that it seemed to me like 'what is the big deal about making that change?' But after reading the section it changed my mind a little. It does not meet the IAU's criteria...and after discovering all those other dwarf planets in the Kuiper belt it made it so there was a whole new category to which Pluto was a better fit."

"I'm not a professional astronomer I don't have a Ph.D. in planets (clearly) so I think it could be either way. I don't have significant knowledge to make a case on it being a planet or not. Whomever classified Pluto as a dwarf planet obviously knows what they're doing."

"It really doesn't make or break my day, Pluto could spiral into a black hole and it wouldn't make much of a difference to me."

"I'm exactly sure, but I'm going to guess that, Pluto should be classified as a planet because it orbits the sun, it is round and it dominates its orbit."

"Because that's what I was raised knowing, and now it is all ruined."

"Since I was a kid I always was told that Pluto was a planet, but now people are saying it is not. So whether it is a planet or not, I still will consider it a planet mentally."

"If Pluto was a planet, then it wouldn't have been fair to the other Kuiper belt objects--they would get jealous and they'd all have to join the planet list, and it'd be a mess."

"When scientists discovered a thousand bodies that are similar to Pluto, that made it not unique. Even though Pluto was a lot bigger than all of the other bodies, but there's usually going to be outliers in data, especially when you have 1,000 separate pieces of data. On the other hand, for something to be classified as a planet it needs to be 'large enough to have its gravity pull them into spherical shapes.' I went with neutral because I feel the 'dwarf planet' name is a good enough middle ground for Pluto."

"Pluto should not be a planet because there's plenty of other dwarf planets just like it. We should not keep Pluto as a planet because of tradition--science is about evolving!"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"It seems to me that most other terrestrial planets, and the moon, receive frequent battering by meteorites and asteroids. Why do we not see more of this on Earth? are we just lucky all the time?" (Not lucky, it's just that Earth has had so much tectonic plate motion to fold over any surfaces with these original impact craters down into the mantle.)

"Do greenhouse gases ever go away once in the atmosphere?" (Only if gravity is not enough to prevent them from leaking up out into space, or if there are oceans that can soak them up and incorporate them into sedimentary rock that tectonic plate motion eventually push down into them mantle.)

"I want to go to Mars really bad."

"How much of the first three quizzes will be on the midterm? I am really looking forward to a review day to kind of tie all of this information together." (The first midterm will be comprehensive, but a very selective study guide will be posted soon. Review day will be next week.)

"I've noticed the past two quiz scores for everyone in the class, and no one has gotten a perfect score (40/40). Have you considered curving the scores?" (The scores are curved--remember that the grading scale has 70% for a "B." Keep in mind that everyone should get close to a 100% for the in-class activity points, and the online reading assignment points (which together are worth two letter grades). Also, there have already been a number of perfect scores on North County campus this semester, so step it up, San Luis Obispo campus.)

"I saw you had cartoons on your website and read some of them. I also noticed that a lot of them are over ten years old, any plans for new ones?" (Eventually, but you guys keep me amused enough for now.)

"What is your ultimate favorite hobby or activity outside of teaching?" (Dancing and DJing swing music with Mrs. P-dog.)

"How do you feel about Pluto being demoted?" (Did we talk about grandfather clauses in class already? If I haven't already, let me tell you my personal feelings about this.)

Online reading assignment: double-slit interference

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on double-slit interference.

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Based on the reading and the presentation, I understood that the double slit experiment demonstrates the wave nature of light. The path difference starts out in phase but travels different paths to reach the screen, and so the pattern presented on the screen shows the alterations between constructive interference and destructive interference."

"This chapter was pretty straightforward about describing double slit in phase interferences and the multiple parts of it such as maxima and minima, different lengths, wavelengths and angles."

"I feel that I understand the basics on the information presented in the textbook and the blog, such as what the maxima and minima are and what the difference is between d and D."

"By dispersing the light rays through two slits causes the light to act constructively and destructively depending on the distance each wave of light has to travel until it meets the other at a given point. When the distance allows for a whole integral multiple of the original wavelength, the light is constructive and more intense. When the waves are related by an odd number of 1/2 wavelengths, the light waves are destructive to each other and cancel each other out."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"Nothing was really confusing about this section and assigned reading."

"I don't think I know what D is. Or how to find it."

"I found most of the information presented in the textbook and blog to be confusing and could use some further explanations or lecture on this material. I am mainly confused on how to apply this information to problems or why we would."

"All the numbers seem reasonable enough, but for some reason, I can't really see the conceptual picture if I was to be asked a question pertaining to this section of the chapter. It shouldn't be too big a deal, but I'm usually able to figure things out much faster if I can paint a picture in my head of what's going on. Think just more pictures would help remedy this."

"I found the variables to be confusing after considering the reading and example questions in the book. I am familiar with what they stand for but would benefit from examples so I understand what the definitions and variables really mean with respect to the slits and screen."

"I did not understand a lot from the reading and the presentation. The only thing I really understand is how to find the path length difference ∆l using d·sinθ."

"I am confused as to when to use the double-slit interference equation. I also don't fully understand the Young's double-slit experiment that is explained in the textbook."

Explain the difference between "maxima" and "minima" in double-slit interference.
"The difference between maxima and minima is that maxima is the max intensity at the screen which is produced by a constructive interference while minima is the minimum or zero intensity at the screen produced by a destructive interference."

"Either constructive (maxima) or destructive (minima) interference occurs when we solve for different θ angles."

"Maxima interference is constructive and is at points where the light rays have a path difference of whole integral wavelengths. Minima are deemed by destructive behavior by waves with odd integrals of 1/2 wavelengths."

Explain the difference between the two distances in double-slit interference, d and D.
"The centers of the slits are separated by a distance of d, and the separation of the slits from the screen are a distance of D."

As defined for double-slit interference, the range for possible θ angles is:
–180° to +180°.  ** [2]
–90° to +90°.  ************************** [26]
0° to 180°.  * [1]
l0° to 360°.  [0]
(Unsure/lost/guessing/help!)  ***** [5]

Describe what x is used to measure in double-slit interference.
"It is used to measure the position on the screen."

"x is used to measure the distance between the center maxima fringe and the adjacent bright fringe."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"If the light wave is passing through a vertical slit, does that mean that only half of the light intensity is making it past the first screen?" (That would only be true for polarizers with "slits" that are approximately the same size as the wavelength of light passing through. For visible light, the sizes of the slits are immensely larger than the wavelengths, so the slit would behave as a conventional "window" rather than a polarizer.)

20140225

Online reading assignment: runaway planets, jovian planets, and dwarf planets (oh my!) (NC campus)

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on runaway planets (Venus and Mars), jovian planets (Jupiter, Saturn, Uranus and Neptune), and the dwarf planets (and the International Astronomy Union classification scheme).

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"I find it interesting to take a look at each planet separately and their about their various differing and similar attributes. Really fascinating to me!"

"I found it interesting that Venus is so like Earth when it comes to mass and they are both relatively close to the sun, but their surfaces are completely different."

"The fact that a shield volcano on Mars is the size of Missouri."

"For a while I assumed that Mars was red because it was hot, I didn't realize it was just the coloring of the minerals on its surface."

"How Jupiter atmosphere goes from gas to liquid as you go deep into the planet and the two elements don't necessary have a boundary between each other."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"When thinking about surface age, I find that I have to think carefully about the processes taking place such as: lava flow, large impact craters, small craters to determine which came first, second and last. I have to slowly visualize the process in my mind. that's how I learn best."

"Global warming has always been a littler confusing. I never totally understood why there was global warming."

"When thinking about surface age, I find that I have to think carefully about the processes taking place such as: lava flow, large impact craters, small craters to determine which came first, second and last. I have to slowly visualize the process in my mind. that's how I learn best."

"I found it a little confusing why Neptune has more atmospheric circulation than Uranus even though it is farther from the sun."

Identify the relative amounts of these characteristics for Venus, compared to Earth. (Only correct responses shown.)
Volcanic outgassing, up until now: about the same as Earth [50%]
Heat from the sun: more than Earth [78%]
Amount of atmosphere, today: more than Earth [61%]
Interior core heat, today: about the same as Earth [22%]
Geologic activity, today: less than Earth [67%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Volcanic outgassing, up until now: less than Earth [55%]
Heat from the sun: less than Earth [72%]
Amount of atmosphere, today: less than Earth [83%]
Interior core heat, today: less than Earth [77%]
Geologic activity, today: less than Earth [100%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).  *** [3]
Saturn (most prominent rings).  * [1]
Uranus (least active weather patterns).  ********* [9]
Neptune (farthest from the sun).  ***** [5]
(Unsure/guessing/lost/help!)  [0]

I believe Pluto should be a planet.
Strongly disagree.  [0]
Disagree.  *** [3]
Neutral.  ******** [8]
Agree.  ******* [7]
Strongly Agree.  [0]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"I have ALWAYS known Pluto as a planet."

"I remember being really mad in third grade when I couldn't do my planet report on it but if it doesn't fit the criteria then I guess it's out of luck..."

"I'm so sad that Pluto isn't a planet anymore. I did a report on it when I was in fourth grade...that I still have..."

"Pluto is very small--if Eris isn't a planet, Pluto shouldn't be one."

"There are scientific facts to prove why Pluto should not be a planet."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Why does it matter if Pluto is classified as a planet or a dwarf planet?" (Because it really does matter to some people.)

"Do you think Pluto should be a planet?" (Did we talk about grandfather clauses in class already? If I haven't already, let me tell you my personal feelings about this.)

20140224

Online reading assignment: interference

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on interference.

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Speakers are in-phase when they are wired with the same polarity. They are out-of-phase when wired with opposite polarities. Constructive interference happens if the wavelengths of the sound waves produced line up with one another. Destructive interference is when the wavelengths don't line up."

"Not much."

"I understand the difference between interference and diffraction. I remember learned a little bit about this in general chemistry. It's where interference deals with different waves that arrive at our vision in different phases and then diffraction is just the waves traveling around objects."

"I understand really well that constructive interference means the troughs and crests of both waves line up. Destructive interference means that the troughs and crests line up with the other waves crests and troughs. Constructive interference is a good sound while destructive will be silence or a quiet sound."

"For two in phase speakers where one wave travels a half-wavelength longer than the other, the path difference is (1/2)·λ, and as a result crests and troughs line up with the other speaker's troughs and crests: destructive interference."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"The equations were quite intimidating."

"All of the equations baffled me, and I am really not sure what I am supposed to take away with this knowledge. The explanations felt over my head. The example was like another language to me!"
"If in phase is called constructive interface why is there destructive too in in phase sources. I'm confused about why there is both constructive and destructive in both in phase and out of phase sources and how you can tell the difference besides looking at a stereo system and matching the wires by color. Other than that example in the blog I don't understand what the definition is of out of phase, I am assuming it is the same as destructive in which one wavelength is half a wavelength ahead of the second."

"I'm not really sure how to tell the difference between constructive and destructive interference. I think I'll be okay after some examples though."

Figure 25-4
Giambattista/Richardson/Richardson, Physics, 2/e, p. 926
McGraw-Hill, 2009

Identify the characteristics of the sources, waves, and interference type. (Only correct responses shown.)
Sources: in phase [32%]
Path length difference: odd number of half wavelengths [68%]
Interference: destructive [65%]

Figure u12lb11
Light Waves and Color--Lesson 3: The Path Difference
The Physics Classroom

Identify the characteristics of the sources, waves, and interference type. (Only correct responses shown.)
Sources: in phase [80%]
Path length difference: integer number of wavelengths [80%]
Interference: constructive [86%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"When designing stadiums for concerts do they take this into account and use physics to make sure the crowd hear the best constructive sounds?" (Well, maybe not for stadiums, but certainly for auditoriums and concert halls, especially taking into account reflections and reverberation.)

"When finding the path differences one can have constructive and destructive for either in phase sources and out of phase sources when doing a problem to find path difference--how can you tell when it is in phase or out of phase?" (The relative phase of the sources would be explicitly stated in a problem; or you would be given everything else, and be asked to determine the relative phase of the sources.)

"In a sound-canceling microphone, what happens when there are multiple waves from different frequencies?" (These typically can only destructively interfere with a constant amplitude, constant frequency ambient sound, such as a jet engine, etc., all other sounds would be unaffected.)

"I was a little confused about why constructive and destructive interference is different for in phase sources and out of phases sources. Can't you just apply the definition and know whether it's constructive or destructive?" (Yes, but "carefully.")

"m is any integer?" (Yes.)

"This is unrelated to this chapter but I heard about the Higgs boson and tried to Google it and am very confused but would like to know more about it." (You can't go wrong with Ph.D. Comics.)

20140222

Astronomy quiz question: April 2014 total lunar eclipse moon visibility

Astronomy 210 Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

In April 2014 observers in San Luis Obispo, CA will see a total lunar eclipse[*]. When observers in San Luis Obispo, CA[**] are watching this total lunar eclipse, at the same time observers in Paso Robles, CA will see:
(A) a total lunar eclipse.
(B) a partial lunar eclipse.
(C) a normal full moon.
(D) (None of the above choices, as the moon would not be visible.)

[*] http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2014Apr15T.pdf.
[**] N.b.: San Luis Obispo, CA, and Paso Robles, CA are the locations of the main and satellite locations of Cuesta College in San Luis Obispo county.

Correct answer (highlight to unhide): (A)

For a total lunar eclipse, the moon is completely in the umbra of Earth. All observers on the night side of Earth (which would include both San Luis Obispo, CA and Paso Robles, CA, both located within the same county on the central California coast) will be able to see this total lunar eclipse at the same time.

Section 30674
Exam code: quiz02nF09
(A) : 25 students
(B) : 1 student
(C) : 0 students
(D) : 0 students

Success level: 96% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.14

Section 30676
Exam code: quiz02sCt8
(A) : 36 students
(B) : 6 students
(C) : 0 students
(D) : 1 student
(No responses: 1 student)

Success level: 83% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Astronomy quiz question: Venus and Mars as morning stars

Astronomy 210 Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

A view of the horizon is shown below, as seen from San Luis Obispo, CA at a certain date/time. Carefully note the positions of Venus and Mars.


The locations of Venus and Mars are shown in the diagram below (not to scale, and orbits have been simplified as circles instead of ellipses). Which one of the choices (A)-(D) corresponds to the position of Earth? Clearly circle your answer below.


Correct answer (highlight to unhide): (D)

If Earth is at location (D), when a line is drawn from Earth to the sun, the observer at sunrise (6 AM) would see Venus low above the rising sun in the east horizon, and Mars high above the west horizon.


(Placing Earth at location (A) would have Venus and Mars both not visible at sunrise; placing Earth at location (B) would make Venus and Mars both visible low above the east horizon at sunrise; placing Earth at location (C) would only have Venus visible low above the east horizon at sunrise.)

Section 30674
Exam code: quiz02nF09
(A) : 5 students
(B) : 5 students
(C) : 2 students
(D) : 14 students

Success level: 56% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

Section 30676
Exam code: quiz02sCt8
(A) : 4 students
(B) : 6 students
(C) : 16 students
(D) : 18 students

Success level: 43% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.66

Astronomy quiz archive: eclipses/history of astronomy

Astronomy 210 Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz02nF09


Section 30674
0- 8.0 :
8.5-16.0 : **** [low = 9.5]
16.5-24.0 : ******
24.5-32.0 : ********* [mean = 26.3 +/- 8.8]
32.5-40.0 : ******* [high = 40.0]


Section 30676, version 1
Exam code: quiz02sCt8


Section 30676
0- 8.0 :
8.5-16.0 : **** [low = 11.0]
16.5-24.0 : *************
24.5-32.0 : ******************* [mean = 26.1 +/- 6.6]
32.5-40.0 : ******** [high = 36.5]

20140221

Astronomy current events question: Messier 82 supernova discovery

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Oli Usher and David Weston, "Supernova in Messier 82 Discovered by UCL Students," January 22, 2014
http://www.ucl.ac.uk/maps-faculty/maps-news-publication/maps1405
Supernova SN 2014J in the nearby M82 Cigar Galaxy was recently discovered by __________ at the University of London Observatory.
(A) undergraduate students.
(B) robotic software.
(C) comparing archived film negatives.
(D) deciphering Mayan codexes.
(E) a professor's grandchildren.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 40 students
(B) : 1 student
(C) : 4 students
(D) : 1 student
(E) : 2 students

Astronomy current events question: Disk Detective Zooniverse project

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Liz Kruesi, "Help Astronomers Find Dust Disks with New Zooniverse Project," February 2, 2014
http://cs.astronomy.com/asy/b/astronomy/archive/2014/02/02/help-astronomers-find-dust-disks-with-new-zooniverse-project.aspx
The Zooniverse Disk Detective project will use __________ to look for forming planetary systems in NASA images.
(A) internet volunteers.
(B) Google search software.
(C) high-powered lasers.
(D) dark matter detectors.
(E) decommissioned supercomputers.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 32 students
(B) : 0 students
(C) : 3 students
(D) : 9 students
(E) : 4 students

Astronomy current events question: sleeping Jade Rabbit

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Emily Poore, "Sleep of Death for China's Lunar Rover?," January 29, 2014
http://www.skyandtelescope.com/community/skyblog/newsblog/A-Sleep-of-Death-for-Chinese-Lunar-Rover-242585291.html
The Chinese moon rover Yutu ("Jade Rabbit") may not be able to revive itself after the most recent lunar night, when it was designed to __________ in order to survive.
(A) burrow underground.
(B) reconnect with the lander unit.
(C) restart its nuclear reactor.
(D) fold in on itself.
(E) extract magnetic field energy.

Correct answer: (D)

Student responses
Sections 30678, 30679, 30680
(A) : 2 students
(B) : 6 students
(C) : 3 students
(D) : 35 students
(E) : 2 students

20140218

Online reading assignment: magnifiers, optical instruments

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on magnifiers and optical instruments.

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"For microscopes I understand that object 1 becomes image 1 for the objective and then image 1 becomes object 2 for the eyepiece. The same is true for telescopes."

"I got the similarities between telescopes and microscopes: the three basic components (objective lens, tube, eyepiece) and they both produce a real image that becomes object 2 for the eyepiece. Object 1 for a telescope is extremely far away, which differs from a microscope in that its rays hit it as essentially parallel rays."

"I understand the key differences between a microscope and telescope much better now."

"I understand that the angular size is not the actual size. I believe that the angular size is a measure of how big something "seems" from your viewpoint."

"The textbook reading was easy to understand and I get the basic principles and ideas presented on microscopes and telescopes. I also understand the section on angular magnification."

"I understand that the microscope and telescope lenses are all converging lenses. I understand that they differ in that the microscope should have short focal lengths while the telescope should have a short eyepiece focal length and long objective focal length. If these are as short and long as possible, given the instrument, this will optimize angular magnification."

"A magnifier (converging lens) doesn't really magnify by enlarging an object, but it puts the object into focus by putting in on the focal point. A higher angular size means a bigger object seen but to a near point for optimal focus. The final images of microscopes and telescopes are inverted images."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I'm very confused. In all the pictures on the blog all the rays from the first lens converge on the focal point of the second lens so I'm unsure if I'm missing something."

I don't understand--how does a simple magnifier use a converging lens to form an upright image that is larger?"

"I am confused about whether the eyepiece creates an image 2 because it does not look like the lines ever intersect. This is like ray tracing 3 but it doesn't seem right that it will not create an image."
"I don't really understand how the microscope and telescope ray tracings produce an image because light rays hit the objective and produce real images but they fall on the focal point of the eyepiece (similar to ray tracing 3) making no image. I feel like the two should produce ray tracings like 4 or 5 (virtual, enlarged images) because that's what they do."

"From the reading in the textbook and the online presentation from the blog I am confused on the simple magnifier and the ray tracings associated with microscopes and telescopes."

"I am still confused with the ray tracings. I don't understand how to figure out which is which when it comes to microscopes eyepieces and telescopes in general."

"I'm getting confused with the telescope and microscope stuff. I'm confused when we start dealing with more than one lens."

"I am confused by the intermediate images formed and the how the images become the objects for the second lens."

"It was pretty clear and the presentation pictures were very helpful."

Identify the type for each of these lenses. (Only correct responses shown.)
Telescope objective: converging [84%]
Telescope eyepiece: converging [84%]
Microscope objective: converging [91%]
Microscope eyepiece: converging [81%]

Identify the ray tracing for each of these lenses. (Only correct responses shown.)
Telescope objective: ray tracing 1 [38%]
Telescope eyepiece: ray tracing 3 or 4 [47%]
Microscope objective: ray tracing 2 [56%]
Microscope eyepiece: ray tracing 3 or 4 [34%]

A (compound) microscope should have a __________ focal length objective lens and a ___________ focal length eyepiece lens in order to maximize its angular magnification.
short; short.  ********************** [22]
short; long.  ******* [7]
long; short.  **** [4]
long; long.  [0]
(Unsure/lost/guessing/help!)  *** [3]

A telescope should have a __________ focal length objective lens and a ___________ focal length eyepiece lens in order to maximize its angular magnification.
short; short.  [0]
short; long.  **** [4]
long; short.  *************************** [27]
long; long.  ** [2]
(Unsure/lost/guessing/help!)  *** [3]

Identify the tube/barrel length L definitions for these optical instruments. (Only correct responses shown.)
Microscope: distance from inside focal point to inside focal point [61%]
Telescope: distance from lens to lens [53%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I just need to see some stuff on microscopes and telescopes."

"We get to look at microscopes and telescopes in class? Ooo weee!!!"

"What will the ray tracings be like on the quiz?" (Like any of the ray tracings from the converging/diverging lens worksheet.)

Online reading assignment: history of astronomy, telescope powers (SLO campus)

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on problems caused by the atmosphere for telescope observing, Earth, and the impacted worlds: the moon, and Mercury.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"Planets have retrograde motion, because Earth is temporarily passing them as they are all at different different speeds and distances."

"I found it interesting that the higher up you put a telescope, the clearer in image will be. The example used in the power point of trying to look up at the sky while under water was a great example and helped me understand the concept. I also found it interesting that the infrared telescope Herschel Space Observatory was cooled to -453° F."

"I think the observatories on Mauna Kea in Hawaii are pretty cool. I think it is pretty cool because out of all the places is the world it is on the Big Island."

"It was really cool learning about why stars twinkle. I never thought about it really, so it was cool to learn a fact about that."

"I have always wondered about why stars twinkle. I remember a time not to long ago someone told me that they twinkle because of particles in the air. It makes much more sense that it is turbulence. I feel much better now knowing the real reason."
"I think its cool that there are telescopes out there that can reduce twinkling."

"Astronomers no longer have to sit outside on top of a freezing cold mountain, with technology such as CCDs--astronomers can record data from inside a room. I guess I had never thought about astronomers not having that option."

"How our planet has the hottest core. I always assumed that planets like Mars would have a hotter core."

"What was the most interesting to me was in the presentation how it talked about the mass of the planets and how hot their cores are and that the hotter the core the more geological activity. The analogy between Earth and Mercury as a turkey and Cornish hen made it make sense to me. I was wondering though why does mercury have the coldest core when it's closest to the sun. I would think that mercury would be hot since it's close to the sun. I guess it's surface is hot obviously but then why not it's core?"

"I found the adaptive optics interesting because I am highly interested in the idea around stars' twinkling. I think its amazing they have the technology to adjust the image so one can see the size and shape of the star without the effects of twinkling."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The large impact hypothesis was confusing to me. I just really did not understand it."

"I found it confusing on the carbon dioxide and how Earth takes it in and takes it out. Also it confused me about the moon, and how to identify its features from oldest to youngest."

"I haven't quite yet found anything that is particularly confusing. I just need to review before the test."

"Just how they can draw up these hypothesis. It's crazy how they are able to know how much iron is in Mercury without having to go there."

"The video link to the 'Light' video on Vimeo confused me and also scared me a little bit (in a comical sense :D)"

"I was really confused by the difference between active optics and adaptive optics. I don't really understand how either of them work other than they are telescopes that are moved by computers. I couldn't understand the explanation that described what either of them are. I also really did not understand how to tell what features on the moon and mercury were oldest and youngest. I feel like I was missing something because I was that clueless about it. Are we just supposed to be able to tell from the photos? Because I could not."

Stars to appear to "twinkle" in the night sky because of:
"Twinkling is caused by turbulence in Earth's atmosphere, and a star near the horizon, where you look through more air, will twinkle more then a star overhead."

"The air in our sky and its affects on the light's path to our eyes. The turbulence in the sky can cause the light to bend and ultimately distort our vision of the sky above."

"Because we live under an 'ocean of air.' Any disturbance in the atmosphere distorts the view of the night sky, causing 'twinkling.'"

A large modern optical telescope in outer space would have images with better __________ than a comparable ground-based telescope.
brightness.   *** [3]
resolution.  ******************* [19]
magnification.   [0]
(None of the above choices.)  [0]
(Two of the above choices.)  **** [4]
(All of the above choices.)  ************ [12]
(Unsure/guessing/lost/help!)  ** [2]

Identify how carbon dioxide enters and how it is taken out of Earth's atmosphere. (Only correct responses shown.)
Enters from: volcanoes [60%]
Taken out by: oceans [72%]

Identify the oldest (longest ago) to the youngest (most recent) features on the moon. (Only correct responses shown.)
Craters partially filled in with flat lava plains: oldest (formed longest ago) [48%]
Flat lava plains: middle [35%]
Craters on top of flat lava plains: youngest (formed most recently) [70%]

Identify the oldest (longest ago) to the youngest (most recent) features on Mercury. (Only correct responses shown.)
Large crater basins: oldest (formed longest ago) [54%]
Lava-filled lowlands: middle [65%]
Long curving ridges: youngest (formed most recently) [68%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I am having a hard time with all of the new terms. I am not the type of person that can just read 20 vocabulary words in a textbook and understand them. I need to hear them used in class and explained a little better." (An astronomy education researcher once counted the number of glossary words in a one-semester astronomy textbook, and compared it to the number of vocabulary words in a first-semester Spanish language textbook. Guess which had more new words? But yes, we'll be sure to explain and use them properly in class.)

"I feel so insanely overwhelmed with the amount of content in the assigned reading and presentations for this week. Plus I still have to study for the quiz which is about totally different stuff! I'm stressing out hardcore. Help :O" (You've already gone through and answered everything from the flashcard question packet, which is more than nearly everyone else in this class has done to prepare for this quiz, so I think you'll be okay.)

"I am really enjoying the class so far this semester. I am only taking it for a requirement but it has been so much better than that." (Cool. Cool cool cool.)

"P-dog, do you have a dog? If so, is its name D-dog?" (Mrs. P-dog's dog's name is Briquetta, aka "Bricky," "Bricktober," and "Brickhouse." I'm actually more of a cat person.)

"Do you offer extra credit?" (Yes. Later this semester. When you'll need it.)

"You have a hearing aid? If so do you like it?" (It's actually a conduction hearing device to channel sound to my other (good) ear. I hate it, but it's better than nothing. #fml But I do get to claim being the world's deafest swing DJ.)

"You have the same name as my sister. My sister's name is Priscilla and my dad calls her P-dog as a nickname, I swear I didn't make that up."

"Finding the locations of the planets. It was not in the textbook anywhere for me to practice." (That's what the flashcard question packet is for.)

Online reading assignment: history of astronomy, telescope powers (NC campus)

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on problems caused by the atmosphere for telescope observing, Earth, and the impacted worlds: the moon, and Mercury.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"It was very interesting to find out why stars actually appear to twinkle because of the comparison of looking at an image from underwater."

"Light pollution--causing the telescopes to not be able to get as good as an image of the night sky. This led me to think about the locations of very large telescopes, and just how hard it would be for astronomers to get to these telescopes located in these remote mountains."

"I thought it was interesting that Earth has a much larger core than the moon. I thought it was interesting because I had never heard about the large impact theory."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found the electromagnetic spectrum chart confusing. Its kind of hard to interpret and to understand."

"I found it confusing that the greenhouse gasses are controlled by oceans. I just didn't quite understand how the 'recycling' happens."

"The density and size of the planets was confusing for me to grasp. In particular, it's importance to the mass and temperatures of the planetary cores."

Stars to appear to "twinkle" in the night sky because of:
"Stars twinkle because we are seeing them through our own turbulent atmosphere."

"The light from stars has to travel through air which causes the light to bend and changes the way the light looks to our eyes."

A large modern optical telescope in outer space would have images with better __________ than a comparable ground-based telescope.
brightness.   [0]
resolution.  ********* [9]
magnification.   ** [2]
(None of the above choices.)  [0]
(Two of the above choices.)  **** [4]
(All of the above choices.)  ****** [6]
(Unsure/guessing/lost/help!)  * [1]

Identify how carbon dioxide enters and how it is taken out of Earth's atmosphere. (Only correct responses shown.)
Enters from: volcanoes [50%]
Taken out by: oceans [36%]

Identify the oldest (longest ago) to the youngest (most recent) features on the moon. (Only correct responses shown.)
Craters partially filled in with flat lava plains: oldest (formed longest ago) [37%]
Flat lava plains: middle [32%]
Craters on top of flat lava plains: youngest (formed most recently) [23%]

Identify the oldest (longest ago) to the youngest (most recent) features on Mercury. (Only correct responses shown.)
Large crater basins: oldest (formed longest ago) [41%]
Lava-filled lowlands: middle [46%]
Long curving ridges: youngest (formed most recently) [55%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I didn't quite understand the features of the moon and of Mercury. Could really use some clarification on that."

"Can NC students attend a star gazing party in SLO? Does the SLO campus have a bigger telescope?" (Yes, and yes--the Bowen Observatory on SLO campus has a 14" refractor telescope.)

"The textbook said that 'Earth's oceans and plant life' have been absorbing carbon dioxide. If I selected either of those above, am I correct? And the book also said that humans burning the fossil fuels formed by the ocean creates carbon dioxide so does that mean the ocean creates it too?" (Plant life and fossil fuel burning are contributing factors in the removal and sources of carbon dioxide, but the vast overall removal and source of carbon dioxide in Earth's atmosphere are due to oceans (and tectonic motion) and volcanoes.)

20140214

Physics quiz question: wavelength of changed frequency radio station

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 23.7

FM radio station KCPR broadcasts at 91.3 MHz. The closest unused FM frequency for this area[*] is at 91.9 MHz. If KCPR were instead to broadcast at 91.9 MHz, its wavelength would be __________ compared to broadcasting at 91.3 MHz.
(A) shorter than.
(B) the same as.
(C) longer than.
(D) (Not enough information given.)

[*] radio-locator.com/cgi-bin/vacant?select=city&city=San%20Luis%20Obispo&state=CA.

Correct answer (highlight to unhide): (A)

Wavelength λ depends on both the speed v and frequency f:

λ = v/f.

Since the speed of radio waves depends only on the medium (air), and is independent of changes in frequency (ignoring negligible dispersion effects), an increase in frequency would result in a decrease in wavelength.

Sections 30882, 30883
Exam code: quiz01ksB4
(A) : 30 students
(B) : 3 students
(C) : 7 students
(D) : 0 students
(No response) : 1 student

Success level: 73%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.70

Physics quiz question: unpolarized light, different polarizer sets

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 22.45

Unpolarized light is incident on two sets of ideal polarizers.


Compared to polarizer set 1, polarizer set 2 will transmit __________ light.
(A) less.
(B) the same (non-zero) amount of.
(C) more.
(D) (Both polarizer sets will have no light transmitted through them.)

Correct answer (highlight to unhide): (B)

An ideal polarizer will transmit one-half of unpolarized light through it, where the transmitted light would be fully polarized in the same direction as the transmission axis of the polarizer.

From Malus' law, the fraction of polarized light passing through a polarizer is given by cos2θ, where θ is the angle between the original polarization and the transmission axis of the polarizer.

For polarizer set 1, the fraction of light passing through the first polarizer is 0.5, and will have a vertical polarization. The fraction of this light passing through the second polarizer is cos2(45°) = 0.5, and will have a polarization that is at a clockwise angle of 45° with respect to the vertical. Thus the fraction of the original light that passes through both polarizers of polarizer set 1 is the product 0.5·cos2(45°) = 0.25.

For polarizer set 2, the fraction of light passing through the first polarizer is also 0.5, but the resulting light that passes through will have a polarization that is at a clockwise angle of 45° with respect to the vertical. The fraction of this light passing through the second polarizer is cos2(45°) = 0.5, and will have a vertical polarization. Thus the fraction of the original light that passes through both polarizers of polarizer set 2 is the product 0.5·cos2(45°) = 0.25, and thus will transmit the same (non-zero) amount of light as compared to polarizer set 1.

Sections 30882, 30883
Exam code: quiz01ksB4
(A) : 12 students
(B) : 22 students
(C) : 6 students
(D) : 1 student

Success level: 54%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

Physics quiz question: broadcasting from an electric dipole antenna

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 22.1

A radio station uses a horizontal electric dipole antenna oriented east-west. It will broadcast most effectively to the __________ of its location.
(A) north and south.
(B) east and west.
(C) (Both of the above choices.)
(D) (No broadcasting is possible using this electric dipole antenna.)

Correct answer (highlight to unhide): (A)

An electric dipole antenna will broadcast most effectively in all directions perpendicular to its orientation, which for this horizontal east-west antenna would be to the north and to the south of its location (as well as directly overhead, or anywhere in the sky along a north-to-south line). There would be zero signal broadcast to the east and to the west of the antenna, as those locations would be looking at the antenna end-on, and there would be no detectable transverse oscillations.

Sections 30882, 30883
Exam code: quiz01ksB4
(A) : 34 students
(B) : 7 students
(C) : 0 students
(D) : 0 students

Success level: 83%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17

Physics quiz question: speed of light in melted butter

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 23.7

Light in air (index of refraction 1.000) passes into melted butter (index of refraction[*] of 1.45) with an incident angle of 60.0°. (Drawing is not to scale.) The speed of light in melted butter is __________ the speed it has in air.
(A) slower than.
(B) the same as.
(C) faster than.
(D) (Not enough information is given.)

[*] physics.info/refraction/.

Correct answer (highlight to unhide): (A)

The relationships between the index of refraction and speed of light in a given medium are:

nair = c/vair,
nmelted butter = c/vmelted butter.

Since the index of refraction for air is 1.000, the speed of light in air essentially nearly identical to that in vacuum, c. Since the index of refraction for melted butter is greater than that of air, then the speed of light through melted butter must be slower than that in air.
Sections 30882, 30883
Exam code: quiz01ksB4
(A) : 41 students
(B) : 0 students
(C) : 0 students
(D) : 0 students

Success level: 100%
Discrimination index (Aubrecht & Aubrecht, 1983): 0

20140213

Physics quiz question: wavelength of light in air

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 22.19(a)

Light of wavelength 440 nm in crown glass (index of refraction[*] of 1.51) is incident at an angle of 30.0° at the interface between crown glass and air (index of refraction 1.000). (Drawing is not to scale.) The wavelength of this light in air is:
(A) 290 nm.
(B) 440 nm.
(C) 660 nm.
(D) 860 nm.

[*] physics.info/refraction/.

Correct answer (highlight to unhide): (C)

The relations between the index of refraction and the speed of light, for crown glass and for air, are:

ncrown glass = c/vcrown glass,

nair = c/vair,

where the given (or assumed to be known) quantities, unknown quantities, and quantities to be explicitly solved for are denoted. Also the relations between wavelength, speed, and frequency are:

λcrown glass = vcrown glass/fcrown glass,

λair = vair/fair.

However, the frequency of the light in crown glass is the same as the frequency it has in air, such that:

fcrown glass = fair,

vcrown glass/λcrown glass = vair/λair,

λair = λcrown glass·vair/vcrown glass,

λair = λcrown glass·ncrown glass/nair = (440 nm)·(1.51)/(1.000) = 664.4 nm,

or to two significant figures, 660 nm.

(Response (A) is (440 nm)/(1.51); response (D) is (440 nm)/(0.51).)

Sections 30882, 30883
Exam code: quiz01ksB4
(A) : 8 students
(B) : 4 students
(C) : 27 students
(D) : 2 students

Success level: 66%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58

Physics quiz archive: electromagnetic waves, reflection/refraction

Physics 205B Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz01ksB4



Sections 30882, 30883 results
0- 6 :  
7-12 :   * [low = 9]
13-18 :   ***********
19-24 :   ****************** [mean = 22.6 +/- 5.0]
25-30 :   *********** [high = 30]

20140212

Online reading assignment: history of astronomy, telescope powers (SLO campus)

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on reviewing the history of astronomy, Kepler's and Newton's laws, and telescope powers.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"I found how these astronomers figured out all these complicated things out, yet they didn't have any of the technology that we have today."

"I think telescopes are really cool, I've always had a fascination for stars and I used to have a telescope and I am interested in learning more about them."

"I liked the GIF animation from Under The Tuscan Sun and how it was an analogy for the change of perspective in parallax."

"I really enjoy history so I found this weeks reading very interesting. I particularly liked learning more about Galileo and the pope's order for him to face the Inquisition. He was inspiring in that he made discoveries off of observation and was brave enough to believe what he saw instead of what everyone else believed at the time. It was even more inspiring that he stood by that in the face of condemnation. I like scientists with hearts and not just brains. What he did took moral fiber and I respect that."

"I thought the most interesting part of the textbook reading and of the presentation previews was Kepler's laws and Newton's ;aws and the other info about the other astronomers who were the first to discover things about space. I wasn't very familiar with Kepler's laws yet but they made sense to me and provided an explanation for things that I had previously wondered about. I also was very interested in Newton's laws and those were easy for me to grasp because I'm already familiar with them from previous classes. Learning about their laws makes it easier for me to differentiate between them and the other astronomers we are supposed to remember."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found Kepler's laws a little confusing, with some clarification I think I would be fine. What confuses me is how did he come to these conclusions and how did he do so with such rudimentary instruments? Obviously we can see with satellites how planets move now because we have objects in space, but how did astronomers do it before?"

"It's a little difficult to keep straight which astronomer is responsible for a given idea (because there's lots of different astronomers and lots of different ideas). But I'm sure with time and review it will become easier."

"The light gathering information of the telescope is kind of confusing to me still. It is just the wording of the book."

"I found Newton's second law of motion hard to understand and do not get how he got there."

When a planet is undergoing retrograde motion, over several nights it moves __________ with respect to the background stars.
east to west.   *************************** [27]
west to east.  *********** [11]
(Either of the above choices is possible.)   ***** [5]
(Unsure/lost/guessing/help!)  *** [3]

When a planet is undergoing prograde motion, over several nights it moves __________ with respect to the background stars.
east to west.   ************* [13]
west to east.  *************************** [27]
(Either of the above choices is possible.)   *** [3]
(Unsure/lost/guessing/help!)  *** [3]

The __________ powers of a telescope depends on the: (Only correct responses shown.)
light-gathering power: diameter of the primary lens/mirror [72%]
resolving power: diameter of the primary lens/mirror [57%]
magnifying power: both the focal lengths of the primary lens/mirror and eyepiece: [39%]

The least important feature to consider when purchasing an optical telescope is the __________ of its images.
brightness.   ****** [6]
resolution.  * [1]
magnification.   ******************************* [31]
(Two of the above choices.)  * [1]
(Unsure/lost/guessing/help!)  ******* [7]

Briefly explain your answer for the least important feature to consider when purchasing an optical telescope.
"I'm not sure what the least important feature would be. They all seem pretty important to me."

"Images are limited by their resolution, the lower resolution available, the lower quality of image, that is why that is important. Brightness is also important because if the picture is too dark then you won't be able to see anything. Magnification won't matter if those other two features are poor in quality."

"Because it is more important to be able to capture the light than to zoom in on the object."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"What's the policy on missing class again?" (Don't miss too many, as there are no make-up points, but you can miss a few in-class activities and quizzes without having them adversely affect your grade.)

"I'm having a hard time with reading the lectures before class. This week I just didn't get to it but last week I spent a lot of time on it and didn't understand a lot until you explained it in class. Should I be worried?" (That sounds pretty typical, but at least you knew what you didn't understand before coming to class, and were prepared to learn what you needed to learn.)

"My only question is about the donut on a string--I was wondering which law it was; that was the only thing I couldn't figure out."

"Will we get a chance to use the Bowen Observatory upstairs? (Yes, tonight!)

"By the way, I'm on Team Edward from Twilight. Just wanted to throw that out there." (*smh*)

"Are the post-lecture reading assignment and pre-lecture reading assignment supposed to be the same? I did both because I didn't wanna be marked down for missing an assignment." (They are the same, they're just posted twice for redundancy.)

"Sorry that I tend to draw a lot in class...I noticed that I forgot to change/add a few things on that drawing of you and Grumpy Cat, but I still hope you liked it!"

Online reading assignment: corrective optics, magnifiers

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on corrective optics and magnifiers.

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Based on the reading and the presentation I understood that depending on what type of vision defect a person may have, that will determine what type of lens will serve to correct their vision. People with myopia need diverging lenses to correct their vision whereas people with hyperopia need converging lenses."

"When you look through two lenses: If the first lens would have formed a real image past the second lens then the image becomes a virtual object for the second lends. If the first lens forms a real or virtual image before the second lens, then the image is a real object for the second lens. The image formed by the first lens serves as the object for the next lens. Angular magnification is a value of how much larger the angular size of something appears as seen through a magnifier."

"I best understand the process of accommodation. I know that it is when our eye changes to help focus on objects at different distances and that this ability can deteriorate with age."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"The ray tracings are still giving me a lot of trouble."

"The difference between optical power and focal length."

"I found the two-step model to be a bit confusing unless applied to the prescriptions. I would like to go over some other examples we may see using the two-step model."

In general, a converging lens will produce a virtual, upright image located __________ the original object.
closer than.   ******* [7]
at the same distance as.  * [2]
farther than.  ****************** [18]
(More than one the above choices.)   *** [3]
(Unsure/lost/guessing/help!)  ***** [5]

In general, a diverging lens will produce a virtual, upright image located __________ the original object.
closer than.   ******************** [20]
at the same distance as.  [0]
farther than.  ****** [6]
(More than one the above choices.)   ***** [5]
(Unsure/lost/guessing/help!)  **** [4]

Identify the type of lens used for these optics. (Only correct responses shown.)
Glasses/contacts to correct for myopia: diverging [77%]
Glasses/contacts to correct for hyperopia: converging [74%]
Glasses/contacts to correct for presbyopia: converging [40%]
Magnifying lenses: converging [69%]

State the units of optical power for lenses, and briefly describe the relationship between optical power and focal length.
"The units are called diopters and they are equal to the inverse of the focal length."

Explain the difference between the two types of magnification, m and M.
"M refers to the angular magnification, whereas m refers to the transverse magnification. The former is the ratio of the angular size using the instrument to the angular size with the unaided eye, while the latter is the ratio of the image size to the object size."

If an object is brought closer to your eye, its angular size will:
increase.  ************************ [24]
decrease.  ***** [5]
remain unchanged.  ** [2]
(Unsure/lost/guessing/help!)  **** [4]

When a converging lens is used as a simple magnifier, the object is placed at a distance p = __________ in front of (to the left of) the lens.
+∞.  **** [4]
+25 cm (at your near point).  *************** [15]
+f (at the focal point of the lens).  ************ [12]
(Unsure/lost/guessing/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I was confused on this slide from the blog. The one where you can see through the glasses and then around it is blurry. Are the two lenses different but our eyes combine them to make one perfect image?" (The view through the two lenses are shifted probably because of perspective, but yes, there seems to be a slight difference in their optical power, to correct for slightly different vision defects in each eye. Ideally your brain should integrate them together into a single view, but failing that, it may just concentrate on the dominant and/or more corrected eye.)

"The dolls performing optometry tests creeped me out."

"I'LL BE HONEST, I HAVE TWO MIDTERMS TOMORROW AND THURSDAY. I SORRY. ANY POINTS ARE BETTER THAN GETTING A ZERO. :(" (Two midterms this early in the semester--what's up with that? Anyway, good luck with those. Seriously.)