20150131

Astronomy current events question: Andromeda Galaxy stellar populations

Astronomy 210L, spring semester 2015
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!)
Tim Stephens, "Study of Andromeda's Stellar Disk Indicates More Violent History than Milky Way," (January 8, 2015)
http://news.ucsc.edu/2015/01/andromeda-galaxy.html
The Andromeda galaxy may have merged with several smaller galaxies in the past, based on analyzing data from the Keck Observatory and Hubble Space Telescope of its:
(A) central supermassive black hole.
(B) look-back time.
(C) dark matter halo.
(D) gravitational pull.
(E) star velocities and ages.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 5 students
(B) : 3 students
(C) : 4 students
(D) : 14 students
(E) : 34 students

Astronomy current events question: Large and Small Magellanic Cloud edges

Astronomy 210L, spring semester 2015
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!)
David Lee Nidever and Knut Olsen, "NOAO: Smashing Results About Our Nearby Galactic Neighbors," (January 5, 2015)
http://www.noao.edu/news/2015/pr1501.php
The non-uniform edges of the Large and Small Magellanic Clouds observed by the Cerro Tololo Inter-American Observatory (CTIO) in Chile may be debris from:
(A) cosmic background radiation.
(B) supernova remnants.
(C) past interactions.
(D) black hole accretion disks.
(E) dark matter.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 12 students
(B) : 15 students
(C) : 21 students
(D) : 10 students
(E) : 3 students

Astronomy current events question: classification of stellar debris disks

Astronomy 210L, spring semester 2015
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!)
Francis Reddy, "Volunteer 'Disk Detectives' Top 1 Million Classifications of Possible Planetary Habitats," (January 6, 2015)
http://www.nasa.gov/content/goddard/volunteer-disk-detectives-top-1-million-classifications-of-possible-planetary-habitats/
__________ sorted over 1 million potential debris disks surrounding young stars from NASA's Wide-field Infrared Survey Explorer data.
(A) Photoshop filters.
(B) Internet volunteers.
(C) Randomized computer routines.
(D) Computer screensavers.
(E) An artificial intelligence.

Correct answer: (B)

Student responses
Sections 30678, 30679, 30680
(A) : 4 students
(B) : 39 students
(C) : 3 students
(D) : 1 student
(E) : 14 students

20150130

Online reading assignment: total internal reflection, polarization

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 total internal reflection and polarization.

The reflection of the fish is upside-down.  Does that make sense?

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.
"I understand that two conditions are required for total internal reflection to occur, including the ray of light in a higher refractive index material is incident on a material with a lower refractive index; and the incident angle in the higher refractive index material is greater than the critical value."

"Polarizers only allow polarized light to pass through if the polarized light matches the transmission axis of the polarizer."

"When particles oscillate in an unorganized fashion, the light emitted is unpolarized. On the other hand, a radio antenna would be a perfect example of a polarized light source, because the particles oscilate up and down in a vertical motion, such that the light will have vertical polarization."

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 found the 'frustrated refraction' concept very confusing. I had a hard time understanding the diagram that came with it."

"I have a hard time visualizing what is happening when reading the blog and textbook. I get mixed up when the text describes transmitted and incident angles and could use some examples or visual aids to picture how the light is reflecting on the higher and lower index materials. I think I am just getting mixed up with vocabulary."

"I'm not entirely sure how to draw the orientation of the transmitted polarized light."

If the incident angle of a light ray is less than the critical angle, the light ray will be:
reflected.  *** [3]
transmitted.  ************************ [24]
(Both of the above choices.)  ******** [8]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  *** [3]

If the incident angle of a light ray is greater than the critical angle, the light ray will be:
reflected.  ************************ [24]
transmitted.  ***** [5]
(Both of the above choices.)  ** [2]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  ****** [6]

Total internal reflection is possible when a light ray in a __________ medium hits a boundary with a __________ medium.
faster; slower.  ************* [13]
slower; faster.  ******************** [20]
(Both of the above choices.)  [0]
(Unsure/guessing/lost/help!)  ***** [5]

A vertical antenna will emit __________ polarized light.
horizontally.  ** [2]
vertically.  ***************************** [29]
(Both of the above choices.)  *** [3]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  *** [3]

Horizontally polarized light can be received by a _________ antenna.
horizontal.  ***************************** [29]
vertical.  ***** [5]
(Both of the above choices.)  [0]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Second week of school almost complete. Gosh how time flies when you are having fun doing physics."

"Please explain the differences between reflected, transmitted, and totally internally reflected rays...slowly." (O...k...a...y... Seriously, though, we'll keep doing more examples in class today.)

"Please go over polarization! And I though I understood the three different cases of total internal reflection...but now I'm questioning myself and need some clarification please!" (Yes, there will be enough time in class to follow up on questions you have on the reading assignment.)

"Will equations be given to us on quizzes and exam like last year?" (Yes, in fact the same set of equations that will be on the quizzes and exams are always listed on the last page of every worksheet packet.)

"Can you go over the practical applications section and the correct answers for these questions?" (As time allows, we can go over detailed solutions for the most problematic responses on the reading assignments. Also, don't forget that the answers to every reading assignment are posted the next morning on this blog (via Twitter hashtag #CuestaPhys205B).)

20150128

Online reading assignment: flipped classroom, motions and cycles (SLO campus)

Astronomy 210, spring semester 2015
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 Earth's rotation/precession/revolution/tilt, the moon's motions and cycles, and watching two video presentations on the flipped class: "What Is the Flipped Class?" and "How the Flipped Classroom Works."

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 the section on seasons to be very interesting. I had never put too much thought into how the seasons worked. The summer and winter solstice was pretty cool to read about, and the book did a good job with pictures and examples of how seasons happen."

I find the concept of precession interesting because it has such dramatic effects. It is pretty amazing to thing that 4,800 years ago, the Egyptian records show that the celestial pole was the star Thuban. Now the pole is switching toward polaris. And in another 12,000 years the pole will have moved toward Vega."

"I had no idea that the north star was constantly changing, i just always thought it was the same star."

"I thought it was interesting that Earth wobbles while it rotates on its axis and takes approximately 26,000 years to complete one cycle. I never knew this information before I only knew that Earth rotated every 24 hours."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found 'pole wandering' to be somewhat confusing because I couldn't really wrap my head around that concept. Is there not always an exact assigned North Star?"

"The difference between rotation and revolution are kind of confusing, but I think it's just going to take examples and some memorization on my part to fully grasp it."

"The textbook says that in January we would see the sun in front of the constellation Sagittarius, and in March it would be in front of Aquarius. Being someone who is intrigued by the zodiac signs and when they correspond with certain months of the year, I'm confused as to why they are different with the sun. Because Sagittarius is December and March is Pisces and Aries...so does it have to do with different planet placement? Stars? The moon?"

What date would Virgo be just above the east horizon, as seen by an observer at 11 PM in San Luis Obispo, CA? (Ignore daylight saving time.)
February 20.  **************************** [28]
April 25.  [0]
July 4.  [0]
August 20.  *** [3]
(Unsure/guessing/lost/help!)  ** [2]

Match these cycles with their approximate duration.
(Only correct responses shown.)
Earth's rotation: 24 hours [94%]
Earth's revolution: one year [100%]
Earth's precession: 26,000 years [100%]
The moon's revolution: one month [94%]

Place these moon phases in chronological order in their cycle (starting with new moon).
(Only correct responses shown, in unscrambled order.)
New moon: first [94%]
Waxing crescent: second [76%]
First quarter: third [76%]
Waxing gibbous: fourth [73%]
Full moon: fifth [91%]
Waning gibbous: sixth [76%]
Third quarter: seventh [73%]
Waning crescent: eighth [70%]

Explain what is different about homework in a flipped class.
"For homework you go over what you're going to do in the next class meeting."

"Students do their homework at school with the teacher. This allows the teacher to spend more one on one time with the student answering questions and explaining things a little more in depth."

"Homework in a typical class is normally a second look at the information that we have already gone over in class. It's usually a good to to study and get to better know the material. In this flipped class, we are going over the material for the first time. I'm not sure is that will be a good or a bad thing for me. I wouldn't know if my brain was taking in the information the way it was meant to. I might make sense of the material in a different way and feel good about what I know, if I'm still doing the readings and putting in the work."

"This is the first time I've ever had homework like this online. Usually teachers have you turn in written homework."

Describe where/when most student learning occurs in a flipped class.
"Most learning occurs at home, doing homework. Class time is used for clarification and questions."

"In a flipped classroom, most learning is happening pretty equally inside and outside of class. The students have the ability to learn what's going to be discussed prior to class, learn even more information during the class, and then extend their knowledge after class as well."

"On my own time, but I definitely need to hear and see the instructor explain everything in order to feel confident in understanding the material."

"Students learn in the classroom more than they do outside the class."

"It happens at home rather than class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"The wording and jargon in this textbook is flying over my head. I can kind of understand what it's explaining....but not really. It needs to be described by a living person that knows what they're talking about... Will you spend a good amount of time explaining in class?" (As needed, where needed. That's why I need you to show me specifically what you understand, and what you are confused on before coming to class, even if it's nothing...or everything.)

"A flipped classroom isn't the best way for me to learn. I like to read the material before going to class and preview the online presentations but I would miss the lectures. For me the best way to learn is to read the material, listen to a lecture that goes into more detail/ explains what the material is, then to work in group activities. I'm not the best at teaching myself." (While there just isn't time to lecture on everything during class, there will still be some time devoted to traditional lecture in class, but selectively on what the class is most interested in and/or confused on.)

"I really appreciate your effort to make the class fun and interactive, a three hour lecture would be too dry and who really has the attention span for three hours of straight lecture. I am impressed with your website too, hands down the best professors’ site I have seen so far. Good layout and easily accessible. Pondering the true size and scale of Earth in respect to our known universe, and the fact that there is even more we do not know, makes me feel insignificant and suicidal." (Thanks. And dang, those are some deep thoughts.)

20150127

Online reading assignment: flipped classroom, motions and cycles (NC campus)

Astronomy 210, spring semester 2015
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 Earth's rotation/precession/revolution/tilt, the moon's motions and cycles, and watching two video presentations on the flipped class: "What Is the Flipped Class?" and "How the Flipped Classroom Works."


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.
"That the North Star is not always the same star as probably most people think. The North Star changes due to precession, because I like watching movies with plots dated far back in time where the people back then would have looked to the stars, mainly the North Star, for navigation."

"What I found was most interesting was that the reason why it is cold in the winter and hot in the summer, is because of the angle at which the sun is pointed towards us. I thought it was interesting because you can always see the sun during the day, I just didn't know what exactly makes the days hot, and other days cold."

Learning about moon phases--I didn't know about all the different names crescent, gibbous, waning , waxing. I only new about new moon and half moon or full moon."

"It is crazy to think we are always moving even though it might not feel like it."

"I had no idea that there was such a thing as a 'moonth' which is where we get the 'month' from. I also found it interesting that the direction that Earth's axis tilt changes through 26,000 year cycles. I had no idea it changed at all. I did know it was tilted though."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I don't really get why zodiac signs have to do with anything in astronomy."

"I had trouble with the moon phases. It's probably more of a memorization issue,but I couldn't get a grasp on which came first and how the moon is supposed to look when its waning, waxing, or first or third quarter."

"Not sure exactly what the celestial sphere looks like. I know it's a scientific model but I didn't see any pictures of what it is."

What date would Virgo be just above the east horizon, as seen by an observer at 11 PM in San Luis Obispo, CA? (Ignore daylight saving time.)
February 20.  *********************** [23]
April 25.  * [1]
July 4.  [0]
August 20.  *** [3]
(Unsure/guessing/lost/help!)  ******* [7]

Match these cycles with their approximate duration.
(Only correct responses shown.)
Earth's rotation: 24 hours [94%]
Earth's revolution: one year [91%]
Earth's precession: 26,000 years [97%]
The moon's revolution: one month [88%]

Place these moon phases in chronological order in their cycle (starting with new moon).
(Only correct responses shown, in unscrambled order.)
New moon: first [97%]
Waxing crescent: second [65%]
First quarter: third [82%]
Waxing gibbous: fourth [65%]
Full moon: fifth [88%]
Waning gibbous: sixth [65%]
Third quarter: seventh [77%]
Waning crescent: eighth [65%]

Explain what is different about homework in a flipped class.
"Homework contains the material and/or lecture that would have been presented within a normal class period."

"You are able to access slides and videos that were in class. Therefore, you can go back and see them as many times as you'd like."

"We basically teach ourselves at home, and then in class you clarify things we couldn't figure out and teach us based on our responses to the questions you give us."

"Homework in a flipped classroom is assigned after a class in preparation for the next class time. During class you go over any questions."

Describe where/when most student learning occurs in a flipped class.
"In the class."

"I would think at home."

"It seems as though it occurs in the classrooms where the instructor can individually tend to the needs of the students. Also it can occur at home where the students have time to watch the videos or the assigned lesson in a way that is more productive and beneficial towards their academic success."

"The student goes over lecture material at home and then preforms 'homework' in class. Therefore the student first attains this knowledge at home but then applies it in the classroom, the application of knowledge is when it becomes solidified in the students mind."

"Most of the learning in a flipped classroom happens at home anytime before class. The classroom is where the knowledge is applied in activities and questions are answered."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I like the flipped classroom's approach to homework. It allows me to find where I need help, but with the added bonus of knowing I can get the clarification I need in the next class."

"The flipped class method is different, however, I'm excited to see if I can learn better with the flipped class method rather then the normal teaching method."

"I really like your teaching style and how you left it to the class to make policy." (Thanks. And now it's on you guys to enforce the technology policy (or cut others slack.)

"The textbook stated that people in Australia are not be able to see the same stars and constellations that we do here at home. Does this mean that star charts vary and are dependent on your location to be used accurately?" (Yes. Even if you got a little north or south of SLO just in the northern hemisphere, you would need a slightly different starwheel for those locations.)

"Do these questions have to be about the assignment or are they about any random question we can think of (that is appropriate)?" (You just did.)

20150126

Flashcard question: technology use policy in class (spring semester 2015)

Astronomy 210, spring semester 2015
Cuesta College, San Luis Obispo, CA

"I Forgot My Phone"
Charlene deGuzman and Miles Crawford
http://youtu.be/OINa46HeWg8

After showing a short movie depicting the pervasiveness of smartphone use at the start of the semester, students in introductory astronomy classes at Cuesta College were asked a subjective question regarding their attitudes towards texting and social networking smartphone use in class. This is part of a think-pair-share activity using flashcards to answer syllabus quiz questions.

Astronomy 210
Section 30674 (NC campus)

Making/receiving phone calls is acceptable behavior in class.
Strongly disagree:  ************** [14]
Disagree:   ********** [10]
Neutral:   ************* [13]
Agree:   *** [3]
Strongly agree:   [0]

Using laptops/tablets is acceptable behavior in class.
Strongly disagree:  [0]
Disagree:   [0]
Neutral:   ******* [7]
Agree:   ***************************** [29]
Strongly agree:   *** [3]

Texting/messaging/social networking is acceptable behavior in class.
Strongly disagree:  *** [3]
Disagree:   ************** [14]
Neutral:   ************************** [26]
Agree:   * [1]
Strongly agree:   ** [2]


Astronomy 210
Section 30676 (SLO campus)

Making/receiving phone calls is acceptable behavior in class.
Strongly disagree:  ************ [12]
Disagree:   ************************* [25]
Neutral:   ******** [8]
Agree:   [0]
Strongly agree:   * [1]

Using laptops/tablets is acceptable behavior in class.
Strongly disagree:  * [1]
Disagree:   * [1]
Neutral:   ***************** [17]
Agree:   ********************** [22]
Strongly agree:   ********** [10]

Texting/messaging/social networking is acceptable behavior in class.
Strongly disagree:  *** [3]
Disagree:   *********** [11]
Neutral:   ************************** [26]
Agree:   ***** [5]
Strongly agree:   **** [4]


Students were asked to share their responses during the following whole-class discussion, citing examples of legitimate (family obligations, work-related messages, class-related research), as well as disruptive use (ringtones, games, blatant frivolous apps) of smartphones during class.

These responses and student opinions were then used to set the policy, via consensus, regarding texting and social networking during class time.

Previous posts:
  • Flashcard question: texting/social networking in class (fall semester 2014).
  • Flashcard question: texting/social networking in class (spring semester 2014).
  • Flashcard question: texting/social networking in class (fall semester 2013).
  • Flashcard question: texting/social networking in class (fall semester 2011).
  • Online reading assignment: electromagnetic waves, reflection and refraction

    Physics 205B, spring semester 2015
    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 electromagnetic waves and redirecting light (reflection and refraction), along with advice from students from the previous semester, and videos on the flipped class mode of instruction used in this course.

    To convince yourself that the frequency of the wave remains constant in either material, try this with a friend--when a crest appears from the left edge of the screen, say 'in.'  When a crest disappears at the right edge of the screen, have your friend say 'out.'

    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.
    "The electromagnetic spectrum covers all types of light, and visible light is only a very small portion. Different types of light differ by their frequency values, and radio waves have the lowest frequency, and gamma rays have the highest frequency."

    "The difference between independent and dependent parameters when determining wavelength, speed, and frequency."

    "Reflection is redirected light bouncing off a surface. Refraction is light passing through a transparent surface and is redirected by being 'bent.'"

    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 don't understand why the light refracts the way it does as it passes between mediums. I understand that the light slows down, but not why that produces the effects that it does."

    "I did not find anything confusing about the assigned reading or the presentation preview. Although it would be helpful to see the equations used in problems."

    "The equation for index of refraction. Would it be possible to do some examples in class?"

    "I'm having some difficulty with Snell's Law and the concept of how the transmitted ray can become manipulated. I know that it depends on the medium's index of refraction..but this all is a little too unclear for me."

    Consider light traveling either through air (nair = 1.0) or through water (nwater = 1.33). Light travels with the faster speed through:
    air.  *********************************** [35]
    water.  ** [2]
    (There is a tie.)  *** [3]
    (Unsure/guessing/lost/help!)  ** [2]

    A ray of light has an incident angle of 60° in air, and a transmitted angle of 36° in plastic. Determine what happens to each of the following parameters as the light passes from air into plastic.
    (Only correct responses shown.)
    speed v: decreases [71%]
    frequency f: remains constant [55%]
    wavelength λ: decreases [40%]

    For the above example of light incident in air being transmitted into plastic, __________ has the greater index of refraction.
    air.  *** [3]
    plastic.  ******************************** [32]
    (There is a tie.)  [0]
    (Unsure/guessing/lost/help!)  ******* [7]

    A ray of light has an incident angle of 20° in plastic, and a transmitted angle of 29° in air. Determine what happens to each of the following parameters as the light passes from plastic into air.
    (Only correct responses shown.)
    speed v: increases [60%]
    frequency f: remains constant [52%]
    wavelength λ: increases [40%]

    For the above example of light incident in plastic being transmitted into air, __________ has the greater index of refraction.
    air.  ************************** [26]
    plastic.  ********* [9]
    (There is a tie.)  * [1]
    (Unsure/guessing/lost/help!)  ****** [6]

    State your preference for denoting the inverse sine operation.
    Arcsin.  *** [3]
    sin-1.  ******************************* [31]
    (No preference.)  ****** [6]
    (Unsure/guessing/lost/help!)  ** [2]

    Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
    "I've learned that I need to keep myself updated on everything that happens in class and keep up with the homework and reading. There is no time to distract myself. Also how this course will be functioning from now on. Lecture time will be time to ask questions."

    "I want to see some problems in class and show how to use the formulas in different problems, because sometimes I don't get what formula to plug in."

    "Are questions from the reading assignments or the textbook more similar to your exam questions?" (Previous semesters' exam questions are similar to the exam questions you'll be seeing this semester. We'll go over them in class, and last year's exams are also posted on the course website.)

    20150125

    Physics midterm question: Plexiglas®-oil refraction

    Physics 205B Midterm 1, fall semester 2010
    Cuesta College, San Luis Obispo, CA

    Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 23.8

    "olio extra vergine"
    Jim (MyArtistSoul)
    http://flic.kr/p/6NqXvq

    A beam of light in Plexiglas® strikes the interface between Plexiglas® and olive oil, with an incident angle of 60.0°, and a transmitted angle of 61.2°. (Drawing is not to scale.) Light has a faster speed traveling through:
    (A) Plexiglas®.
    (B) olive oil.
    (C) (There is a tie.)
    (D) (Not enough information is given.)

    Correct answer (highlight to unhide): (B)

    Snell's law relates the indices of refraction with the incident and transmitted angles:

    nplexiglas·sin(θplexiglas) = noil·sin(θoil),

    and the indices of refraction for both materials related to the speed of light through them:

    nplexiglas = c/vplexiglas,

    noil = c/voil,

    where the given (or assumed to be known) quantities, unknown quantities, and quantities to be explicitly solved for (or compared) are denoted.

    From Snell's law, because θplexiglas is smaller than θoil, then nplexiglas is greater than noil. From n = c/v, since oil has a smaller index of refraction, it will have a faster speed of light. This can be explicitly seen by substituting the relations for each index of refraction into Snell's law, and relating the speed of light in oil to that in Plexiglas®:

    (c/vplexiglas)·sin(θplexiglas) = (c/voil)·sin(θoil),

    voil = vplexiglas·(sin(θoil)/sin(θplexiglas)) = vplexiglas·(sin(61.2°)/sin(60.0°) = 1.01187178523·vplexiglas,

    Thus to the proper significant figures, the speed of light in oil is one percent faster than in Plexiglas®.

    Student responses
    Section 70856
    (A) : 5 students
    (B) : 6 students
    (C) : 0 students
    (D) : 0 students

    Success level: 55%
    Discrimination index (Aubrecht & Aubrecht, 1983): 0.67

    Physics quiz question: air-Pyrex® refraction

    Physics 205B Quiz 1, fall semester 2011
    Cuesta College, San Luis Obispo, CA

    Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 22.8

    "Ides of March Haul - Pyrex Patented May 27, 1919"
    Fearless Stumbler
    http://flic.kr/p/9qK4PZ

    A beam of light strikes the interface between air (index of refraction 1.000) and Pyrex® (index of refraction[*] 1.474), with a transmitted angle of 38.0°. (Drawing is not to scale.) The incident angle in air is:
    (A) 25.8°.
    (B) 42.7°.
    (C) 56.0°.
    (D) 65.2°.

    Correct answer (highlight to unhide): (D)

    [*] http://physics.info/refraction/.

    Snell's law relates the indices of refraction with the incident and transmitted angles:

    nair·sin(θair) = nPyrex®·sin(θPyrex®),

    where the given (or assumed to be known) quantities, unknown quantities, and quantities to be explicitly solved for are denoted.

    Directly solving for the incident angle in air:

    sin(θair) = (nPyrex®/nair)·sin(θPyrex®),

    θair = sin-1(nPyrex®/nair)·sin(θPyrex®)) = sin-1((1.474/1.000)·sin(38.0°)) = 65.1600804828°,

    or to three significant figures, the incident angle in air is 65.2°.

    (Response (A) is θPyrex®/nPyrex®; response (B) is sin-1(1/nPyrex®); and response (C) is (nPyrex®/nair)·sin(θPyrex®).)

    Student responses
    Section 30882
    (A) : 0 students
    (B) : 1 student
    (C) : 0 students
    (D) : 7 students

    Success level: 88%
    Discrimination index (Aubrecht & Aubrecht, 1983): 0