Online reading assignment: Kirchhoff's laws (SLO campus)

Astronomy 210, spring semester 2020
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 Kirchhoff's laws.


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 it interesting that the emission spectrum relates to the material we learned in class a few weeks ago about gaseous elements. Before, I was only aware that particular colors of light are exclusively emitted depending on the movement of electrons in an element. However, I now know light can be emitted as also a continuous or emission spectrum. I found this interesting because it did not occur to me that a star or even a rainbow might emit photons differently due to their specific spectrum types."

"I find the different spectra interesting. It interests me to know how different things put out different types of light and to learn the science behind it. I always knew that neon lights were different from normal lights, but understanding how they produce their colors is an experience!"

"The spectrum types are very interesting, albeit confusing, from reading about it on my own. It seems like something that will take some further explanation and repetition to get down, but I am interested in exploring it further as light is all around us."

"I enjoyed learning about the different spectra and what produces them. I only knew about the continuous spectrum, so learning about the other ones was very interesting."

"Something I found interesting was the spectra of the sun and stars. This was interesting to me because I didn't know how the spectra was made, and the process is very intriguing."

"I have always found the Doppler effect super-interesting. It is just such an interesting and curious effect. After reading this, it makes a lot more sense."

"The Doppler effect is interesting to me because you can interact and hear it everyday. I think it's really cool that a pitch of sound is determined by its wavelength."

"I really liked learning about the Doppler effect. I never really paid attention to the different pitches a horn makes as it is moving past someone. I think it is interesting that it changes depending on if the car is moving towards you or away from you."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I have a good understanding on the three different types of light spectrum; however, I seem to be struggling with correlating them to actual pictures of objects. When they are shown in the boxed diagrams it is easier to distinguish them, but I'm not sure how to transfer that over to real-life objects."

"I was having a little difficulty debating which things went with emission and absorption spectra, I think I might be getting them backwards, but I also might be right! Lol"

"The three kinds of spectra and their rules.It is hard for me to conceptualize things that I have not heard of before."

"The overview of Kirchhoff's laws in the textbook were too brief and vague."

"The blueshifts and redshifts confuse me because I do not understand the definitions given in the textbook."

"I found it interesting to learn about the Doppler effect but it was more difficult for me to understand. Seeing the wavelengths that a car sound makes when driving past you helped me better understand it since it was drawn out."

I believe Pluto should be a planet. (Original responses.)

Strongly disagree.	* [1]
Disagree.	************ [12]
Neutral.	************ [12]
Agree.	******** [8]
Strongly Agree.	* [1]

I believe Pluto should be a planet. (This is a follow-up question.)

Strongly disagree.	**** [4]
Disagree.	************* [13]
Neutral.	********** [10]
Agree.	***** [5]
Strongly Agree.	* [1]

Briefly explain your answer to the previous question (whether Pluto should be a planet).

"I don't disagree nor agree. I find that the neutral position is easier and shows that the decision of planet making is not mine."

"I agree it should be a planet because it has everything other planets have like being round."

"I agree Pluto should be a planet because it has all the same aspects other planets have like being round."

"It doesn't fit the new definition of what a planet is but lots of people who don't know that definition still call it a planet, so I'm fine with either or."

"I know now that Pluto should not be a planet. It just doesn't fit the criteria."

"I don't really have a strong opinion on whether Pluto should be a planet or not, but based off the evidence it doesn't seem like Pluto fits into the 'planet' category to well. Pluto's orbit and size differ a lot from all of the other planets, it really doesn't seem to fit in."

"After learning the guidelines for what constitutes a planet, it is clear that Pluto does not qualify as one. Though, I don't feel to strongly about it, I wouldn't mind seeing it make a comeback, though that would require a lot of changes in planet definitions."

"I'm neutral. I grew up knowing Pluto was a planet and then became a star, so for me Pluto will always be a planet at heart."

"I believe that if we found life or movement on Pluto we could possibly consider looking into it becoming a planet. However, like I previously said Pluto shouldn't become a planet because its not in the orbiting rings."

"I believe that if we found life or movement on Pluto we could maybe consider looking into it becoming a planet. However, like I previously said Pluto shouldn't become a planet because its not in the orbiting rings."

"Due to it being a body that orbits the sun and it's a dwarf planet."

"I understand why Pluto is no longer considered a planet, because it doesn't dominate its orbit, but since I grew up thinking it was a planet, it is hard for me to view it as anything different. it doesn't fit under the standards of being a planet after learning it doesn't dominate its orbit."

"Pluto should not be a planet because there is many other similar sized dwarf planets in the Kuiper belt that are not considered planets either."

"I do not think it's a planet. But I’m still neutral because I'm willing to listen to someone's views on why it is one."

"Pluto doesn't dominate its orbit so it can’t be a planet. Based off the three classifications for being a planet, Pluto meets all 3. It should be considered a planet, no matter how small it is."

"If Pluto could be a planet then so many others could be too. We would be back in a time with 1,500+ planets and more discovery would lead to more and more. Having a three-step classification narrows down the most important ones to watch."

"Since it was once a planet, I think that it should always be a planet. Although it is known as the dwarf planet, when I first learned about planets it was there, so I will always think it is still considered a planet."

"I don't believe that Pluto should be a planet, and redefining it as a dwarf planet was the correct choice. If it dominated its own orbit around the sun, and didn't come in so close to the moon, and then further than anything else."

"Pluto is too small and boring."

"According to the classifications that we learned about, it doesn't make sense to treat it as a planet."

"Pluto had a good run, we should give Makemake a chance at planethood."

"The classifications makes it a dwarf planet due to it not dominating its orbit."

"I believe Pluto should be a planet because it's more of a planet than Jupiter."

"I still do not believe Pluto should be considered a planet because it cannot expel objects from its own orbit. I believe this fact alone is convincing because asteroids are not considered planets for the same reason. All objects in space must be evaluated with the same set of IAU rules, meaning Pluto's failure to meet these criteria technically would imply it is not a planet."

"Well, I now know how planets are categorized and by following that Pluto is a dwarf planet."

"Pluto can't be a planet, because it does not dominate its own orbit. It fits all the other qualifications for being a planet, except for the fact that it doesn't dominate its own orbit. Therefore, it is considered a dwarf planet."

"The rules are too strict for being a planet."

"Pluto should not be a planet because it does not dominate its orbit, therefore it should be a dwarf planet based on the IAU classes and rules."

"I don't have much of a preference because the logical part of me sees why it's a dwarf planet because it doesn't hit all the criteria of being an independent planet but there's also a part of me that wants Pluto to belong with the other major planets in our system since the little guy is so far away and is already isolated."

Match the spectrum type with their appearance.
(Only correct responses shown.)

Rainbow containing all colors: continuous [85%]
Rainbow with thin black lines: absorption [76%]
Colored lines on a black background: emission [79%]
Given off by hot, dense object: continuous [70%]
Given off by hot, diffuse gas atoms: emission [67%]
Passing through cool, diffuse gas atoms: [52%]

Hot, molten metal produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	********** [10]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	********* [9]
(Unsure/guessing/lost/help!)	******* [7]

The sun produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	******** [8]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	************* [13]
(Unsure/guessing/lost/help!)	***** [5]

The lights atop the Fremont Theater in San Luis Obispo, CA, produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	*********** [11]
emission; series of bright lines on a dark background.	************** [14]
absorption; series of dark lines on a rainbow background.	****** [6]
(Unsure/guessing/lost/help!)	** [2]

Your instructor produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	******* [7]
emission; series of bright lines on a dark background.	*************** [15]
absorption; series of dark lines on a rainbow background.	*** [3]
(Unsure/guessing/lost/help!)	******** [8]

The balrog from The Lord Of The Rings: The Fellowship Of The Ring produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	*** [3]
emission; series of bright lines on a dark background.	***************** [17]
absorption; series of dark lines on a rainbow background.	**** [4]
(Unsure/guessing/lost/help!)	********* [9]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link). The loudness of the car horn:

starts loud, then gets quieter.	**** [4]
starts quiet, then gets louder.	***** [5]
starts quiet, gets louder, then goes back down to quiet.	*********************** [23]
starts loud, gets quieter, then goes back up to loud.	[0]
(Unsure/guessing/lost/help!)	* [1]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link, same as above). The pitch (high note/low note) of the car horn:

starts high, then drops lower.	************* [13]
starts low, then goes higher.	**** [4]
starts low, goes higher, then drops back down to low.	************ [12]
starts high, goes lower, then goes back up to high.	*** [3]
(Unsure/guessing/lost/help!)	* [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"The spectrum picto-quiz was a bit challenging for me, can we find a way to go over these?"

"How do you differentiate between the different spectrums in terms of the examples that were given? I guess I'm still a little confused about their real-life applications and how each works."

"I was hoping you could provide a little more clarification on distinguishing what spectrum is being seen. I had trouble figuring out the ones that were different from the exact examples given when explaining what produces what spectra."

"I'm concerned on how learning the material more on my own will be with it all being online because the lectures were the most helpful with making me understand material."

"Are you happy going completely online? Do you think there is a chance of us maybe coming back to school if this all clears beforehand? I do NOT like all online at all." (I'm okay with it, but it is a lot of work (but I'm finally getting around to learning how to use Adobe Premiere Pro, which I've always wanted to do). As much as I would like us to return back to face-to-face classes before the end of this semester, I'm rather pessimistic about that happening.)

"Online is going to be different, but good." (I appreciate your optimism.)

"Have you ever taught this course online before? Pros and cons?" (No, this is my very first time. I'm having to learn a lot very quickly, it reminds me of when I first started teaching at Cuesta College.)

"I don't know if I'll be fine in an online class since I learn more face-to-face when you explain these things to us."

"I really appreciate the option of 'unsure/lost/guessing/help' on these questions, and I think its a fair choice for assignments like this. However, I think students have the tendency to guess an answer instead of choosing 'unsure/lost/guessing/help' in order to greatly increase their chances of getting lucky and getting points. This is just something that crossed my mind. I know you appreciate knowing if students genuinely don't understand a question or concept, so I am just wondering if this tendency might skew the feedback." (Everyone gets credit for answering a question, whether they get it correct, incorrect, or choose 'unsure/lost/guessing/help.' I think choosing 'unsure/lost/guessing/help' is actually a very honest way of students letting me know that we need to focus on certain topics in class.)

"Will there still be a tutor available for this class now that it is fully online?" (I've asked about that; still waiting to hear from the Student Success Center if tutors will be available online.)

"Thank you for your work in this difficult time." (You're welcome. Thank you all for being patient and willing to change over to learning online.)

"I hope you are staying healthy!" (You, too! #socialdistancing)

"Do you use Spectrum internet?" (Ironically, yes.)

Online reading assignment: Kirchhoff's laws (NC campus)

Astronomy 210, spring semester 2020
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 Kirchhoff's laws.


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.

"How heat can be measured by color. This was interesting to me because you only really think of 'red-hot.' Not much about any other colors."

"This was a rather confusing chapter..."

"The assigned textbook reading was interesting to me because I didn't understand the different forms of light before. I think it's interesting how there is a continuous spectrum, absorption spectrum, and an emission spectrum. I learned something new about light and it was interesting."

"Something I found out that was really interesting to me that I learned from the reading was the Doppler effect for sound and light. It was interesting learning that longer wave lenghths have low pitches and shorter wavelengths have higher pitches, and vice versa with light having the blueshift refer to shorter wavelengths of light and a redshift with longer light wavelengths."

"To learn why car horns sound different when they come towards you and pass you. It's something you don’t really think about much."

"I found the Doppler effect on light from stars interesting, I never knew the way they were moving affected the way we see them."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I didn’t really understand how stars and absorption relate to each other. I know that they start with continuous light from the center but that's where I stopped understanding."

"The Doppler effect, the explanation in the textbook was hard to follow."

"I originally found the stuff on the spectra confusing, because I had trouble distinguishing between the different types at first, but now I think I know them all."

"I do not understand how to really tell the different spectra of light-producing objects. I do not know what I am really looking for."

"Colors in general are hard for me to grasp. Being color deficient makes this lesson hard to learn visually."

I believe Pluto should be a planet. (Original responses.)

Strongly disagree.	*** [3]
Disagree.	******* [7]
Neutral.	********** [10]
Agree.	***** [5]
Strongly Agree.	*** [3]

I believe Pluto should be a planet. (This is a follow-up question.)

Strongly disagree.	* [1]
Disagree.	******** [8]
Neutral.	***** [5]
Agree.	** [2]
Strongly Agree.	[0]

Briefly explain your answer to the previous question (whether Pluto should be a planet).

"It has been considered a planet but I don’t think it really matters if it is or isn't."

"I still believe that Pluto should not be a planet. The IAU had a definition of planets that was too loose and Pluto doesn't fit the criteria."

"It doesn't dominate it's orbit, and it's smaller than our own moon. Pluto does have moons which I think makes a pretty good case for it, but not having enough mass to dominate it's orbit is important in hindsight."

"I don't feel any particular way. As long as we continue to study the planets and make scientific progress."

"I have no strong opinion."

"I don't think that Pluto should be a planet because it doesn't follow the guidelines to be considered a planet."

"The way they classify a planet is very sound."

"I think that Pluto still deserves to have the label as a planet because I think it would be a really cool planet to have in a solar system and it has all the qualities a planet needs besides being in charge of its own orbit."

"I don't feel as strongly that Pluto needs to be a planet. In addition, I agree that we needed better, standardized methods for organizing what is and isn't a planet."

"Now that I learned what defines a planet I now understand Pluto doesn't classify since it does not dominate its orbit."

"I know that Pluto does not classify as a planet with the new rules. But there is still some satisfaction/niceness to still calling Pluto a planet"

"It doesn't meet the criteria to be a planet."

"Due to the newer definition of what a planet is, Pluto just doesn't qualify, it doesn't dominate its orbit 3/14/2020"

"I'm still neutral because it honestly doesn’t matter to me. I understand why it's a dwarf planet now with it sharing its orbit but it doesn’t matter to me if Pluto is a planet or not."

"Pluto does not meet the criteria to classify as a normal planet because it does not clear its orbit."

Match the spectrum type with their appearance.
(Only correct responses shown.)

Rainbow containing all colors: continuous [94%]
Rainbow with thin black lines: absorption [75%]
Colored lines on a black background: emission [69%]
Given off by hot, dense object: continuous [75%]
Given off by hot, diffuse gas atoms: emission [75%]
Passing through cool, diffuse gas atoms: [75%]

Hot, molten metal produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	********** [10]
emission; series of bright lines on a dark background.	** [2]
absorption; series of dark lines on a rainbow background.	*[1]
(Unsure/guessing/lost/help!)	*** [3]

The sun produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	* [1]
emission; series of bright lines on a dark background.	****** [6]
absorption; series of dark lines on a rainbow background.	******** [8]
(Unsure/guessing/lost/help!)	* [1]

The lights atop the Fremont Theater in San Luis Obispo, CA, produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	**** [4]
emission; series of bright lines on a dark background.	********* [9]
absorption; series of dark lines on a rainbow background.	** [2]
(Unsure/guessing/lost/help!)	* [1]

Your instructor produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	**** [4]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	*** [3]
(Unsure/guessing/lost/help!)	** [2]

The balrog from The Lord Of The Rings: The Fellowship Of The Ring produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	***** [5]
emission; series of bright lines on a dark background.	***** [5]
absorption; series of dark lines on a rainbow background.	** [2]
(Unsure/guessing/lost/help!)	**** [4]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link). The loudness of the car horn:

starts loud, then gets quieter.	** [2]
starts quiet, then gets louder.	** [2]
starts quiet, gets louder, then goes back down to quiet.	*********** [11]
starts loud, gets quieter, then goes back up to loud.	[0]
(Unsure/guessing/lost/help!)	* [1]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link, same as above). The pitch (high note/low note) of the car horn:

starts high, then drops lower.	****** [6]
starts low, then goes higher.	[0]
starts low, goes higher, then drops back down to low.	******* [7]
starts high, goes lower, then goes back up to high.	* [1]
(Unsure/guessing/lost/help!)	** [2]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Do you think that making all classes go online was an overreaction? Like I went to work today, everything is still relatively normal in Paso Robles." (At this point everyone is going to come down with COVID-19; but social distancing is meant to stretch out the number of people who are sick at the same time (instead of letting everyone get sick at the same time). So, social distancing is the new norm, right now, for times like this. #flattenthecurve)

"I'm so lost with this chapter!"

"How do I take real situations measuring color and heat and apply it. All sources seem to be different. Is there a trick?" (I've posted a "spectra survival guide" video lecture on Canvas for that.)

"Will we find out what we got on our midterms online through Canvas since we aren't meeting in class anymore?" (Yes, although you can still see the midterm scores online on the old website.)

"What's your favorite part about space?" (Teaching about it, then watching students "get it.")

"How are we going to do lectures now that we are online and is it for the rest of the semester?" (I'll make videos and provide notes for the lectures, and make them available online on Canvas. All assignments (including a new discussion board) will be on Canvas as well, along with the quizzes and exams.)

"What's a blackbody spectrum and where is it mentioned? I don't remember seeing it." (It's a different name for a continuous spectrum (which is given off by hot, dense objects, which are also known as "blackbodies.")

Online reading assignment: double-slit interference

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a bi-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.

"For in-phase sources, the difference in path length will be a whole number of wavelengths for constructive interference. For destructive interference the path difference will be (a whole number plus) a half of a wavelength."

"The presentation did a good job at conveying the path differences for the double slits. It was defined clearly."

"I understand from this section that the maxima and minima of a double-slit interference means whether or not it is constructive or destructive. this is determined by various variables of a double-slit interference like the wavelength, distance between slits, etc."

"Young's double-slit experiment showed how two monochromatic light sources could interfere constructively and destructively. This was shown by the alternating dark and light fringes on the screen he used."

"The difference in lengths that parallel waves travel is equal to their separation distance d between multiplied by sinθ. The inner wave also travels farther."

"In double-slit interference θ is measured from the horizontal and ranges from –90° to +90° with 0° deg being horizontal. The equation dsinθ is used to find the difference in path lengths traveled by two sets of waves. Whether the resulting wave is constructive or deconstructive depends on the whether there is a whole or and a half difference in path lengths."

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.

"Maxima and minima were confusing. double-slit interference was more difficult to understand."

"Definitely the picking the correct information to match the equation. All these symbols are confusing."

"The 'Train of Pain' is still a little confusing, just need to a little more with it."

"I understand the equations and the idea of the path lengths pretty well, but I might need some more practice using and applying them."

"I would benefit from homework examples that have to do with calculating the maxima and minima values to acquire a greater understanding of their relationship to the central bright spot."

"I pretty much understood everything, especially the basics. I might need some polishing of some concepts but that's it."

"Nothing at this time."

Explain the difference between "maxima" and "minima" in double-slit interference.

"The resulting constructive interference is the maxima, and the resulting destructive interference is the minima."

"A maxima is where it is brightest and a minima is where it is least bright."

"Maxima refers to the bright fringes while minima refers to the dark fringes."

Match the double-slit parameter with its symbol. (Only correct responses shown.)

Distance between slits: d [74%]
Any positive or negative whole number: m [74%]
Distance from slits to a projection screen: L [49%]
Wavelength of light passing through both slits: λ [83%]
Difference in paths for light passing through both slits: d·sinθ [51%]
Position along screen, as measured from the centerline: y [46%]

Identify the characteristics of the sources, path difference, and interference type. (Only correct responses shown.)

Sources: in phase [97%]
Path difference: integer number of wavelengths [100%]
Interference: constructive [97%]

Identify the characteristics of the sources, path difference, and interference type. (Only correct responses shown.)

Sources: in phase [89%]
Path difference: odd number of half wavelengths [94%]
Interference: destructive [94%]

Identify the characteristics of the sources, path difference, and interference type. (Only correct responses shown.)

Sources: in phase [97%]
Path difference: integer number of wavelengths [77%]
Interference: constructive [74%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Would like to review these last two diagrams in or after class."

"Are you going to go over this in class?" (Yes.)

"Will we be doing the double-slit experiment in lab?" (Yes.)

"Since the light that passes through the double slits is from a source that is side-by-side and in-phase with the same wavelength, won't the light passing through the two slits always be in phase?" (Well, yes, unless one wave has to travel a further distance than the other wave in order for them to meet at a receiver.)

"I'm not sure how to use the formula ∆l = dsinθ. In which case will the path difference be a whole wavelength or half a wavelength?" (Well, just calculate ∆l for a given θ direction, then see if it is equal to m·λ or (m + 1/2)·λ.)

"I think that in regards to Young's double-slit experiment, when two light paths interfere constructively they create a bright fringe, and when they interfere destructively they produce a dark fringe... is that correct?" (Yes.)

"I was a little confused whether the double-slit experiment only works when the light sources are side-by-side. If you have two separate sources of light that are constructive but that differ in distance does the double-slit experiment still work?" (Yes, but the sources must have exactly the same wavelength, and be in phase with each other. For visible light the most practical way to do this is to have a laser illuminate two side-by-side slits simultaneously.)

"I would benefit from some practice problems."

"Going to try my hardest to make it tomorrow."

Online reading assignment: diffraction

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a bi-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 diffraction.


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 when you decrease the size of W, then the theta or spread increases, and visa versa, increasing W would lead to a more narrow spread, which helps with telescopes. I also understand how waves can bend around the edges of the slit, not just shining directly through."

"Diffraction is the bending of light waves around obstacles or edges of an opening. As light moves through a slit, it will result in an angle that will vary depending on the size of the opening. As the W (width) of the slit increases in size, the angle of light expelled decreases. As W decreases, the angle will increase."

"Diffraction is the bending of waves around obstacles. I also understand that the degree of bending in light is much less than in sound."

"The diffraction minima is given by W·sinθ = m·λ where W is the width of a single slit, θ is the angle of the spread from the center, and λ is wavelength of light."

"Diffraction is how light is perceived and bends through a slit. What is important is how large the wave length is and what the angle it is exiting from the slit at compared to the 'normal.' As the slit increase, the minima angle decreases and vice versa. When talking about telescopes, they use a large width so the angle must be small to resolve details of far-away objects."

"Essentially, decreasing slit width W causes an increase in the 'spread' of the half-angle θ. Conversely, increasing slit width would produce the opposite effect onto the spread of θ."

"The slit width and analogies were perfect. The example in the ocean with the waves is both a pun and a great example! "

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 dark fringes for single-slit diffraction was confusing to me."

"I guess I didn't really understand what a slit is."

"I am confused about how to find the minima angle. I am also unsure of where it comes in and if it is only with destructive interference."

"I was confused about the midpoint of a central bright fringe. I did not understand what that had to do with the destructive interference. "

"What is the difference between spread angle and diffraction minima?"

"I am slightly confused as to what effects the relationship of slit width and spread of theta cause. Looking at the telescope example, I believe I understand the idea that a larger slit with produces a smaller theta causing less spread and a more refined image."

"I'm not understanding the diffraction of light through the telescope, and the hair laser example."

"Not much really. A few examples and minor explanation should get me up to speed."

"I didn't find anything confusing about this topic. "

"Honestly just haven't got to this yet."

Match the single slit parameter with its symbol. (Only correct responses shown.)

Width of a single slit: W [94%]
Wavelength of light passing through the slit: λ [97%]
Direction, as measured from the centerline: θ [97%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"May you explain the textbook diagrams in class? The textbook's diagrams and graphs made the concept more difficult."

"Light without diffraction would pass straight through a narrow slit without spreading out?"

"By making the slit width larger and larger does there reach a point where making the slit larger would result in an inconsequential reduction in the spread of the diffracted waves?" (Yes. If the slit were large, then diffraction (the "wrapping around the edge effect") would be less noticeable, and the light would not seem to spread out much, so the beam would have the same size/shape as the slit. If the slit were very small, then the "edge effect" would be more noticeable, and the light will spread out more such that the beam would "fan out.")

"What is the m referring to in the equation sinθ=m·λ/W), as explained by the textbook? Will there ever be a time when m will be more than 1?" (Yes, in order to find the fainter dark fringes off to the side of the "spread angle" (where m = 1), but we'll only concentrate on the light contained within the m = 1 "spread angle," because that's where most of the spread-out light is concentrated after passing through the slit.)

"I was curious as to what happens when two slits are close to each other. Can they have constructive interference?" (Yes, provide that each slit is small enough that light will spread out (diffract) so they will overlap with each other, and then can interfere with each other.)

"I am glad you're my professor. My other class I felt so lost the whole time but this semester I don't."

Physics quiz question: comparing blue, yellow laser frequencies

Physics 205B Quiz 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

"laser3.jpg"
©CrystaLaser
https://www.crystalaser.com/new/yellowlaser.html

Blue laser light has a wavelength of 445 nm light in air, while yellow laser light has a wavelength of 594 nm in air. The __________ laser light has a higher frequency in air.
(A) blue.
(B) yellow.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

Wave speed v depends on the properties of the medium. Frequency f depends on the properties of the source. These two parameters can be varied independently of each other.

The wavelength λ is the parameter dependent on both of the independent parameters:

λ = v/f.

Since the two laser light colors have the same speed v (as they travel through the same medium), then because of their different frequencies, they will have have different λ wavelengths (as this parameter depends on both the wave source and the properties of the medium):

λ₁ = v₁/f₁,

λ₂ = v₂/f₂,

where λ₁ < λ₂, as blue light (here, λ₁) has a much shorter wavelength than yellow light (here, λ₂). Since v₁ = v₂ (as both forms of laser light travel through the air), then f₁ > f₂, and thus blue laser light has a higher frequency than yellow laser light.

Sections 30882, 30883
Exam code: quiz01PxP7
(A) : 22 students
(B) : 8 students
(C) : 5 students
(D) : 0 students

Success level: 63%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.67

Online reading assignment: standing waves

Physics 205A, fall semester 2019
Cuesta College, San Luis Obispo, CA

Students have a bi-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 a presentation on standing waves.


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.

"Thick strings have lower fundamental frequencies than thinner strings when they are plucked."

"I understand that the fundamental frequency of a string depends on the wave speed v (which depends on its tension and thickness), and length L. The frequencies that this string will resonate at are then merely integer multiples of the fundamental frequency."

"What I understand is some of the standing waves stuff. I know the equation for getting the fundamental frequency of something. I also understand which things are independent and dependent parameters."

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 feel like this is more in depth of the previous waves section, this feels similar and not difficult, just more of it."

"Putting all the different parts together, and not mixing up the independent and dependent parameters."

"I'm having trouble understanding resonance and how nodes are created."

"The difference between node and antinode wasnt as clear to me. Will need some more clarification in class."

(Assuming that their tensions are approximately equal), the __________ strings have a slower wave speed.

thicker.	************************************** [38]
thinner.	*** [3]
(There is a tie.)	** [2]
(Unsure/lost/guessing/help!)	* [1]

After these same-length guitar strings are plucked (assuming that their tensions are approximately equal), the __________ strings vibrate at a lower fundamental frequency.

thicker.	************************************ [36]
thinner.	** [2]
(There is a tie.)	*** [3]
(Unsure/lost/guessing/help!)	*** [3]

After the bass string is plucked, sliding a finger down to decrease its length would __________ the speed of waves along the string.

decrease.	****************** [18]
not change.	******** [8]
increase.	***************** [17]
(Unsure/lost/guessing/help!)	* [1]

After the bass string is plucked, sliding a finger down to decrease its length would __________ the fundamental frequency of the string.

decrease.	*********** [11]
not change.	********* [9]
increase.	********************** [22]
(Unsure/lost/guessing/help!)	** [2]

For standing waves on a string, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)

Wave speed v: independent [59%]
String length L: independent. [43%]
Fundamental frequency f₁: dependent. [50%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"May we focus on the fundamental frequencies? I did not understand the equation."

"Go over deez."

"Is there a particular reason we left waves and then came back to them later?" (We lost a Monday due to Veteran's Day, so we'll pick it up here just before you do the standing waves lab later today. Also this stuff is not on Quiz 6 or on Quiz 7, but you'll see it on the Final Exam.)

"How was your Thanksgiving?" (Eh, it was okay. The day after Thanksgiving went much better.)

"I'm full from the turkey."