Physics midterm question: different light polarizations, same polarizer set

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

A set of two polarizers has either (a) horizontally polarized light, or (b) vertically polarized light incident on it. Discuss why this set of two polarizers will pass through the same fraction of horizontally polarized and vertical polarized light. Explain your reasoning using the properties of light and polarization.

Solution and grading rubric:

• p:
  Discusses/demonstrates that the same amount of light will pass through the set of polarizers as:
  1. the horizontally polarized light is at an angle of 45° with respect to polarizer 1, resulting in cos²45° = (1/2) of this passing through, with a 45° polarization angle parallel to that of polarizer 1; and
  2. the vertical polarized light is also at an angle of 45° with respect to polarizer 1, resulting in cos²45° = (1/2) of this passing through, also with a 45° polarization angle parallel to that of polarizer 1; then
  3. since for both cases (initially horizontally polarized light or initially vertically polarized light) the light that has passed through polarizer 1 has the same polarization angle and intensity, after passing through polarizer 2 the amount of light (and polarization direction) will be same for both cases.
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 26 students
r: 3 students
t: 4 students
v: 0 students
x: 0 students
y: 0 students
z: 0 student

A sample "p" response (from student):

Physics midterm question: wavelengths at total internal reflection interface

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

Light of wavelength 533 nm in a unknown material (index of refraction n₁) undergoes total internal reflection from an interface with a different unknown material (index of refraction n₂). (Drawing is not to scale.) Show that the wavelength in the n₂ material would be longer than 533 nm (assuming that light could eventually be transmitted out in the n₂ material). Explain your reasoning using the properties of light and refraction.

Solution and grading rubric:

• p:
  Discusses/demonstrates that the wavelength λ₂ in the second n₂ material would be longer than 533 nm by:
  1. qualitatively or quantitatively showing that n₂ < n₁ by appealing to the critical angle θ₂ = sin⁻¹(n₂/n₁) (where n₂ < n₁ in order to avoid a domain error in the inverse sine function); or Snell's law n₁⋅sinθ₁ = n₂⋅sinθ₂ where θ₂ = 90°, and thus n₂ < n₁; and
  2. that since index of refraction n = c/v, a smaller index of refraction n₂ results in a faster speed of light v₂; and
  3. since the wavelength λ = v/f, since the second material has a faster speed of light v₂, and the frequency of light is independent of the medium it travels through, then it will have a longer wavelength in that material.
  May combine arguments in (1)-(2) by arguing that total internal reflection occurs when light traveling in a slower material is "frustrated" in trying to travel out into a faster material.
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. Typically one of arguments (1)-(3) missing, incomplete, or problematic.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete. Typically two of arguments (1)-(3) missing, incomplete, or problematic.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying Snell's law and/or critical angles, indices of refraction, wave speed, frequency and wavelengths.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying Snell's law and/or critical angles, indices of refraction, wave speed, frequency and wavelengths.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 17 students
r: 6 students
t: 9 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 3673):
A sample "p" response (from student 1929):

Physics midterm question: second maxima angles not possible

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

A green laser (wavelength 550 nm) illuminates a grating with a unknown spacing between adjacent slits, producing an interference pattern with a first maxima angles of ±32°. (Drawing is not to scale.) Discuss why it is not possible for second maxima angles to be produced by this grating. Explain your reasoning using the properties of source phases, path lengths, and interference.

Solution and grading rubric:

• p:
  Correct. Discusses/demonstrates that the second maxima angle is not possible, by:
  1. solving for the spacing d between grating slits, given the first maxima angle and the wavelength λ of the laser; then
  2. solving for the second maxima angle results in a domain error for the inverse sine function, and interprets this as meaning that the there is no defined second maxima angle.
  (It is possible to use d = λ/sin(32°) from the first maxima equation and insert it into the second equation without explicitly numerically solving for d, such that θ = sin⁻¹(2/sin(32°) for the second maxima angle results in a domain error.)
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. Typically has math errors.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete. Uses minima equation and/or compounded math errors.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying properties of source phases, path lengths, and interference.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying properties of source phases, path lengths, and interference.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 29 students
r: 2 students
t: 3 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1929):
Another sample "p" response (from student 3481):

Physics midterm question: charge to "cancel out" electric field

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

A –3 nC point charge is held at x = 0, such that there is an electric field at x = +4 cm. In order to have no electric field magnitude at x = +4 cm, discuss whether the amount of positive charge to be placed at x = +1 cm should be less than, greater than, or equal to 3 nC. Explain your reasoning using properties of electric forces, fields, and vector superposition.

Solution and grading rubric:

• p:
  Correct. The amount of the (positive) source charge Q₂ must be less than 3 nC in order for the (total) electric field magnitude at x = +4 cm to be zero by discussing/demonstrating:
  1. that the electric field at x = +4 cm of the Q₁ = +3.0 nC source charge pointing to the right (away from this positive source charge) must be "canceled" by the electric field at x = +4 cm of the negative Q₂ source charge pointing to the left (in towards this negative source charge), such that the magnitudes of their respective electric fields must be set equal to each other;
  2. solves for the (negative) amount of Q₂ source charge, which is less than 3.0 nC. (May also place a trial amount of Q₂ source charge to demonstrate that it must be less than (−)3.0 nC in order for its electric field to equal the magnitude of the Q₁ source charge.)
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May not explicitly discuss/demonstrate how the numerical values of the two source charges does not matter.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying properties of electric forces, fields, and vector superposition.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying properties of electric forces, fields, and vector superposition.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 21 students
r: 5 students
t: 6 students
v: 3 students
x: 0 student
y: 0 students
z: 0 student

A sample "p" response (from student 2525):
Another sample "p" response (from student 7744), dropping all common k factors, and common nC and cm units:

Physics midterm problem: diverging lens and converging lens

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

An object 1.0 cm in height is placed 5.0 cm in front of a f = –20.0 cm diverging lens, producing an upright image. This same 1.0 cm high object is then placed an unknown distance in front of a f = +20.0 cm converging lens, producing an inverted image that is the same size as the upright image originally produced by the diverging lens.

Determine (a) the size of the image produced by the diverging lens, and (b) the distance of this object in front of the f = +20.0 cm converging lens.

Show your work and explain your reasoning by using ray tracings and/or thin lens equations, properties of lenses, images, and magnification.

Solution and grading rubric:

• p:
  Correct. Identifies relevant parameters to methodically use the thin lens equation and linear magnification equation, in order to determine:
  1. that for the diverging lens, h_o = +1.0 cm, d_o = +5.0 cm, f = −20.0 cm, and uses thin lens equation to either find d_i = −4 cm (a virtual image) to find image height h_i = +0.8 cm (upright image) from the linear magnification equation, or may eliminate d_i in both equations to solve for h_i directly; and
  2. for the converging lens, h_o = +1.0 cm (the same object), d_o and d_i are both unknown, f = +20.0 cm, and h_i = −0.8 cm (inverted image that is the same size as the upright image produced by the diverging lens), and eliminates d_i in both equations to find d_o = +45 cm. May include very minor math errors with handling fractions and inverses.
• r:
  Nearly correct, but includes minor math conceptual errors, typically overlooking the fact that the image produced by the converging lens is inverted.
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least solves for (1) successfully, and still attempts to methodically use this information in (2) to solve for the object distance for the converging lens. Typically makes multiple conceptual errors, such as overlooking the fact that the image produced by the converging lens is inverted; claiming that the image distance for the converging lens is the same as the image distance for the diverging lens, etc.
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Some garbled attempt at ray tracings and/or thin lens equations, the properties of lenses, images, and magnifications.
• x:
  Implementation of ideas, but credit given for effort rather than merit. No clear attempt at applying ray tracings and/or thin lens equations, the properties of lenses, images, and magnifications.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 4 students
r: 7 students
t: 24 students
v: 0 students
x: 0 students
y: 0 students
z: 0 student

A sample "p" response (from student 7164):

Astronomy current events question: earliest detection of primordial hydrogen

Astronomy 210L, spring semester 2018
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!)

Jennifer Chu, "Astronomers Detect Earliest Evidence Yet of Hydrogen in the Universe" (February 28, 2018)
news.mit.edu/2018/astronomers-detect-earliest-evidence-yet-hydrogen-universe-0228

Primordial hydrogen absorbing light from the universe's first stars was recently detected using:
(A) adaptive optics.
(B) infrared interferometers.
(C) underground neutrino detectors.
(D) radio telescopes.
(E) particle accelerators.

Correct answer: (D)

Student responses
Sections 30679, 30680
(A) : 3 students
(B) : 11 students
(C) : 0 students
(D) : 22 students
(E) : 1 student

Astronomy current events question: oscillation-ejected stars in Milky Way's halo?

Astronomy 210L, spring semester 2018
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!)

Mari-Ela Chock, "Stars Around the Milky Way: Cosmic Space Invaders or Victims of Galactic Eviction?" (February 26, 2018)
keckobservatory.org/recent/entry/halo_stars

Based on analysis of their chemical composition, groups of stars in our Milky Way galaxy's disk may have been knocked out into the halo from oscillations produced by:
(A) matter and antimatter.
(B) type II supernovae.
(C) a passing dwarf galaxy.
(D) the central supermassive black hole.
(E) dark matter.

Correct answer: (C)

Student responses
Sections 30679, 30680
(A) : 3 students
(B) : 3 students
(C) : 24 students
(D) : 5 students
(E) : 2 students

Astronomy current events question: synestia formation of Earth and the moon?

Astronomy 210L, spring semester 2018
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!)

Andy Fell, "How the Moon Formed Inside a Vaporized Earth Synestia" (February 28, 2018)
ucdavis.edu/news/how-moon-formed-inside-vaporized-earth-synestia/

A recent theory proposes that both Earth and the moon formed within a synestia, which is a donut-shaped cloud of __________ formed after the collision of two planet-sized objects:
(A) vaporized rock.
(B) radioactive asteroids.
(C) dark matter.
(D) antimatter.
(E) neutrinos.

Correct answer: (A)

Student responses
Sections 30679, 30680
(A) : 24 students
(B) : 1 student
(C) : 0 students
(D) : 0 students
(E) : 2 students

Online reading assignment question: helpful/unhelpful Midterm 1 physics study tips

Physics 205B, spring semester 2018
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.

Describe something notable that either helped or did not help with studying for this midterm. Selected comments may be discussed in class. (Graded for completion.)

The following are all of the student responses to this question, verbatim and unedited.

"I just work my way through the problems for the subjects I know I have trouble with."

"Don't procrastinate!!! C'mon guys."

"Look at past quizzes, know how to solve a problem from every possible angle."

"The thing that helps the most is the examples of 'p' rubric answers for questions."

"I try to learn and know the material throughout each week. So that I’m not trying to study and stress right before a test. If I know it I know it and I don’t need to over study for it. I just need to preform and show what I know is all..."

"Repetition, repeatedly doing problems that are pertinent to the midterm."

"I have found that it helps to read through all of the example problems and try to figure them out in my head then do them on paper and see how close I got or if I was right. It helps me think through which equations to use for which problems."

"Reviewing the problems from past quizzes as well as some of the more difficult past homework problems. Also, taking notes on each reading assignment when they are assigned helps with studying for the midterm."

"The practice problems help."

"Going over practice problems helps a lot."

"Working through the practice problem set helps!"

"The explanations at the end of each sample problem really help me understand what I need to know or how to approach a problem."

"Just working problems and nailing concepts."

"Reviewing other midterm problems really helps."

"Reviewing old midterm and quiz questions. Reviewing the online notes with my notes to refresh for some questions."

"Going through old reading assignments on the website and going through my notes while actually practicing some of the concepts we went over and keeping them fresh."

"After the review session I was a little bummed to hear the the midterm was going to be more conceptual then actual physics type problems. The idea of trying to apply certain formulas or theories to a problem that you normally wouldn't but you just have to assume that it will work has definitely made studying a little harder for me."

"Don't study what won't be on the test."

"Practice problems over and over again until you're comfortable."

"Doing all the provided practice midterm problems on the website and checking your answer with the correct responses helps prepare for the exam."

"Going over the practice problems can be helpful when preparing for the midterm."

"The blog posts with correct solutions help me understand possible question types and answers that allow me to better prepare."

"Doing all of the review problems, being present and actively participating in lecture."

"I find that doing online midterm questions from past tests (there are quite a few) help a great deal since it helps prepare for the style of questions that might be asked. "

"Being engaged in class is the most helpful thing that can be done to prepare for the exams and quizzes in my opinion."

"I think that the practice problems will help as well as watching Khan Academy videos. My notes have only helped me a little."

"I keep the same routine to study the exams. Every week I rewrite the lesson from the blog and print it. Three days before quizzes, I do all the exercises listed in the weekly plan and label them as (easy, hardcore or reread). Three days before the midterm, I do the same with the prep list of exercises given and I add all the previous ones labelled as 'hardcore.' Two days before, I make a single page of review points. And the day before, I reread all the exercises labelled as it plus my review guide. It is not too much work but all of organization (and I kill a lot of trees too :/ )"

Online reading assignment: stellar parameters (SLO campus)

Astronomy 210, spring semester 2018
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 parallax, distance, apparent magnitude, absolute magnitude, Wien's law and the Stefan-Boltzmann law, and a TED-Ed talk on stellar properties.


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.

"Honestly, I really just loved the TedTalk that you provided as a resource! I just loved hearing about how astrophysicists see the galaxy, and how they study the stars. I loved hearing about the way that light is used to figure out so many things, such as what stars are made out of. It's all just such a big new world for me as someone who's never taken an astronomy class."

"The video of 'How Do We Study the Stars'--it really nicely put everything we'll be covering in the next few weeks with awesome visuals!"

"I liked the YouTube video the best because I find it more fun to learn through hearing someone explain things with visual aids and illustration rather than reading about it."

"I really liked the video. Like, I personally knew all this before but the idea had really good graphics."

"I found it interesting that the brighter stars are ranked with smaller numbers and the dimmer stars are ranked with bigger numbers. I found this to be interesting because it was pretty simple to understand. Also the 'top tier' analogy made it more relatable."

"The measurements of star's brightness, especially thinking about the distance of stars and how it can effect their brightness. the sun being not as bright as most stars is sort of funny to think about as it is the most intense for us."

"That stars that aren't as bright can appear to be, just based on how close they are to Earth. I think this is interesting because for us looking at a star won't actually tell us how bright it is, instead it's like an illusion."

"That you can detect temperatures of stars based off of their colors."

"It's funny how we associate hot with red, but really the lighter colors; blue and white, represent the hottest temperatures."

"To find out that hot objects glow because when they get hot, atoms/molecules get more agitated, which makes them move faster!"

"Learning about the stars--in particular, being able to find the size of the star by luminoscity, color and math! I liked it because it did not seem too strenuous."

"Learning about the different stars and how they are classified by their brightness, color."

"One thing I just genuinely liked about the assigned reading was the mnemonic devices provided, like, 'Only Bad Astronomers Forget Generally Known Mnemonics.' It humanized the science for me a little and made the reading more engaging."

"I'm interested in the different temperatures and luminosity of the stars, as well as the spectral classes."

"Binary systems because I didn't realize that stars could orbit each other. I also thought it was interesting that there could be various ways they can orbit another star."

"How dang smart astronomers must really be. I am obtaining so much new information about astronomy my brain wants to explode. I think its interesting that they can look up and see a star and can tell how hot or cool it is by color and some sort of mathematical equation. It's outrageous!"

"The Stefan-Boltzmann law equation of luminosity, temperature and size is very interesting. I love working with equations."

"The process of finding a star's size."

"Wien's law--the fact that color can tell us so much is amazing."

"Honestly not too much."

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

"I was confused on whether moving a star away would affect its apparent magnitude or the absolute magnitude."

"The difference between apparent and absolute magnitude is confusing between it's not too clear in the presentation."

"I was confused by parsecs, and I am not sure how parallax measurement works."

"I didn't understand how moving a star to 10 pc would put it at a state where it would be at its absolute magnitude?"

"The magnitude scale that is used to measure star brightness is a little confusing to me. I understand the basic ranking, and the absolute magnitude vs the actual magnitude, but the info about the parallax is confusing to me. If there comes a point where I have to discuss it in an essay question response, I think I would struggle. Similarly, I really liked reading about Wien's law and the Stefan-Boltzmann law, but read the end of the presentation where you said to make sure we understand the concept enough to be able to write about it in an exam essay response. This warning made me realize that I might need a little more help just wrapping up the two concepts together neatly to ensure that there aren't any loose ends."

"Something that was confusing is that red does not mean hot, it means the star is cooler. While blue means that it is really hot."

"It gets confusing to me when Wien's law and the Stefan-Boltzmann law needs to be used because it involves math, my least favorite subject."

"I am honestly still confused about why the spectral sequence is out of alphabetical order because it just doesn't make sense, and it bothers me."

"The math."

Explain how apparent magnitude and the absolute magnitude are defined differently.

"The brightnesses of stars when placed 10 parsecs away is their absolute magnitude M, and The apparent magnitude m of a star is the "as is" brightness as seen by an observer on Earth."

"Apparent magnitude measures how bright a star or other celestrial body looks in space. absolute magnitude measures an object, and equals how bright that object would look if it were 10 parsecs, or 32.6 light years away from Earth."

"Absolute magnitude is our view of intrinsic brightness of stars from 10 parsecs away. Apparent magnitude is our view of a star's brightness from Earth."

"Apparent magnitude is how bright an object appears to humans on earth. Absolute magnitude is how bright a star actually, and its intrnsic brightness."

"Apparent magnitude is what we see from Earth. Absolute magnitude puts all stars at 10 parsecs from Earth to accurately compare their magnitudes."

"Apparent magnitude is how we view the star relative to the distance from Earth. Absolute magnitude refers to the legitimate intensity of a star regardless of distance."

"Unsure."

Suppose the sun was moved to a distance of 10 parsecs away. As a result, its __________ magnitude would become dimmer.

absolute.	*************** [15]
apparent.	****************** [18]
(Both of the above choices.)	* [1]
(Neither of the above choices.)	[0]
(Unsure/guessing/lost/help!)	** [2]

Rank the brightnesses of these stars (1 = brightest, 4 = dimmest; there are no ties), as seen from Earth.
(Only correct responses shown.)

1 (brightest): the sun, m = –27 [81%]
2: Canopus, m = –1 [72%]
3: Vega, m = 0 [72%]
4 (dimmest): Kapteyn's star, m = +9 [72%]

Rank the brightnesses of these stars (1 = brightest, 4 = dimmest; there are no ties), if relocated to 10 parsecs from Earth.
(Only correct responses shown.)

1 (brightest): Canopus, M = –3 [58%]
2: Vega, M = +0.5 [72%]
3: the sun, M = +5 [58%]
4 (dimmest): Kapteyn's star, M = +11 [67%]

Determine whether these stars get dimmer or brighter when relocated from their original positions to 10 parsecs from Earth.
(Only correct responses shown.)

The sun: gets dimmer [64%]
Canopus: gets brighter [50%]
Vega: gets dimmer [47%]
Kapteyn's star: gets dimmer [36%]

Rank the temperatures of these main sequence stars (1 = hottest, 4 = coolest; there are no ties).
(Only correct responses shown.)

Hottest: blue main sequence star [72%]
Second hottest: white main sequence star [83%]
Third hottest: yellow main sequence star [64%]
Coolest: red main sequence star [81%]

Rank the temperatures of these supergiant and dwarf stars (1 = hottest, 4 = coolest; there are no ties).
(Only correct responses shown.)

Hottest: blue supergiant [75%]
Second hottest: white dwarf [56%]
Third hottest: yellow supergiant [72%]
Coolest: red dwarf [83%]

Two stars (equally far away) have the same temperature, but one star is dimmer, and the other star is brighter. The __________ star will be larger in size.

dimmer.	***** [5]
brighter.	************************ [24]
(These stars would be the same size.)	* [1]
(Unsure/guessing/lost/help!)	****** [6]

Two stars (equally far away) have the same brightness, but one star is cooler, and the other star is hotter. The __________ star will be larger in size.

cooler.	**************** [16]
hotter.	*********** [11]
(These stars would be the same size.)	* [1]
(Unsure/guessing/lost/help!)	******** [8]

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

"So I know that the hottest stars are blue, followed by white, orange and red. does the same principle apply to the supergiants?" (Yes!)

"Does the fact that a star is a supergiant or a dwarf have an effect on the temperature of the star? I do not think that it does but I am starting to second guess myself." (The temperature of a star depends only on the color; the size of a star is determined from its temperature and its luminosity.)

"I do not understand why a cooler star can be larger in size..."

"I think this section will be a little easier to understand... At least that's what I'm telling myself."

"Please explain more on this chapter. I'm very confused."

"Parallax, arcseconds and parsecs, oh my! I feel like I'm in a Star Wars film and no one told me..."

"No comment." (You just did.)

"The way that this survey complemented the online lecture presentations was really helpful! Having little assignments that really forced us to think about each detail of the larger concepts really helps us to grasp the information that we are being given, and to then apply it!"