Cuesta College, San Luis Obispo, CA
Sections 70854, 70855
Exam code: quiz07VlnC
Sections 70854, 70855 results
| 0- 6 : | * [low = 3] |
| 7-12 : | ********** |
| 13-18 : | ************** |
| 19-24 : | ******************* [mean = 18.9 +/- 6.2] |
| 25-30 : | ******* [high = 30] |
Showing posts with label blackbody. Show all posts
Showing posts with label blackbody. Show all posts
20191204
Physics quiz archive: temperature, thermal equilibrium, heat transfers
Physics 205A Quiz 7, fall semester 2019
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855
Exam code: quiz07VlnC
Sections 70854, 70855 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855
Exam code: quiz07VlnC
Sections 70854, 70855 results
20181205
Physics quiz archive: temperature, thermal equilibrium, heat transfers
Physics 205A Quiz 7, fall semester 2018
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07PeA7
Sections 70854, 70855 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07PeA7
Sections 70854, 70855 results
| 0- 6 : | ** [low = 6] |
| 7-12 : | **** |
| 13-18 : | *********** |
| 19-24 : | ********************** [mean = 20.8 +/- 6.0] |
| 25-30 : | ************ [high = 30] |
20171213
Physics quiz archive: temperature, thermal equilibrium, heat transfers
Physics 205A Quiz 7, fall semester 2017
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07Whu7
Sections 70854, 70855 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07Whu7
Sections 70854, 70855 results
| 0- 6 : | |
| 7-12 : | ******* [low = 9] |
| 13-18 : | ************* |
| 19-24 : | ******************* [mean = 18.9 +/- 5.4] |
| 25-30 : | *** [high = 27] |
20161207
Physics quiz archive: temperature, thermal equilibrium, heat transfer
Physics 205A Quiz 7, fall semester 2016
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07p4sT
Sections 70854, 70855, 73320 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07p4sT
Sections 70854, 70855, 73320 results
| 0- 6 : | * [low = 6] |
| 7-12 : | ************* |
| 13-18 : | *************** |
| 19-24 : | *************** [mean = 18.5 +/- 6.6] |
| 25-30 : | ******** [high = 30] |
20151211
Physics quiz archive: temperature, thermal equilibrium, heat transfer
Physics 205A Quiz 7, fall semester 2015
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07zSOL
Sections 70854, 70855, 73320 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07zSOL
Sections 70854, 70855, 73320 results
| 0- 6 : | * [low = 3] |
| 7-12 : | ***** |
| 13-18 : | ***************** |
| 19-24 : | ****************************** [mean = 21.2 +/- 5.6] |
| 25-30 : | **************** [high = 30] |
20141211
Physics quiz archive: temperature, thermal equilibrium, heat transfer
Physics 205A Quiz 7, fall semester 2014
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07cO4t
Sections 70854, 70855, 73320 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07cO4t
Sections 70854, 70855, 73320 results
| 0- 6 : | |
| 7-12 : | **** [low = 9] |
| 13-18 : | ******* |
| 19-24 : | ******************** [mean = 24.2 +/- 5.5] |
| 25-30 : | ********************** [high = 30] |
20131211
Physics quiz archive: temperature, thermal equilibrium, heat transfer
Physics 205A Quiz 7, fall semester 2013
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07b0o7
Sections 70854, 70855, 73320 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz07b0o7
Sections 70854, 70855, 73320 results
| 0- 6 : | ** [low = 6] |
| 7-12 : | **** |
| 13-18 : | ****************************** [mean = 18.5 +/- 4.8] |
| 19-24 : | ******************** |
| 25-30 : | *** [high = 30] |
20130610
Astronomy in-class activity: star sizes
Astronomy 210 In-class activity 16 v.13.06.10, fall semester 2013
Cuesta College, San Luis Obispo, CA
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet on applying Wien's law and the Stefan-Boltzmann law to determine the relative sizes of select pairs of stars.
(For the purposes of this in-class activity, the proportionality constant in the Stefan-Boltzmann law is omitted, as only relative rather than absolute values of star luminosities, temperatures, and sizes are compared.)
Cuesta College, San Luis Obispo, CA
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet on applying Wien's law and the Stefan-Boltzmann law to determine the relative sizes of select pairs of stars.
(For the purposes of this in-class activity, the proportionality constant in the Stefan-Boltzmann law is omitted, as only relative rather than absolute values of star luminosities, temperatures, and sizes are compared.)
Astronomy in-class activity: Kirchhoff's laws
Astronomy 210 In-class activity 14 v.13.06.10, fall semester 2013
Cuesta College, San Luis Obispo, CA
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet on different spectrum types and Kirchhoff's laws, and on the Doppler effect.
Cuesta College, San Luis Obispo, CA
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet on different spectrum types and Kirchhoff's laws, and on the Doppler effect.
20121214
Physics quiz archive: temperature, thermal equilibrium, heat transfer
Physics 205A Quiz 7, fall semester 2012
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07Di5k
Sections 70854, 70855 results
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz07Di5k
Sections 70854, 70855 results
| 0- 6 : | ***** [low = 3] |
| 7-12 : | ************ |
| 13-18 : | ********************** [mean = 15.2 +/- 5.4] |
| 19-24 : | *********** [high = 24] |
| 25-30 : |
20081020
Astronomy quiz question: continuous spectrum source
Astronomy 210 Quiz 4, Fall Semester 2008
Cuesta College, San Luis Obispo, CA
[4.0 points.] A continuous spectrum is caused by:
(A) blackbody radiation passing through diffuse, cool gas atoms.
(B) electrons moving to lower energy orbitals.
(C) hot, agitated electrons and atoms.
(D) the Doppler effect.
Correct answer: (C)
The electrons and atoms in a hot, dense, opaque object (a "blackbody") will emit a continuous spectrum.
Student responses
Section 70158
(A) : 10 students
(B) : 14 students
(C) : 41 students
(D) : 4 students
"Difficulty level": 63%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55
Cuesta College, San Luis Obispo, CA
[4.0 points.] A continuous spectrum is caused by:
(A) blackbody radiation passing through diffuse, cool gas atoms.
(B) electrons moving to lower energy orbitals.
(C) hot, agitated electrons and atoms.
(D) the Doppler effect.
Correct answer: (C)
The electrons and atoms in a hot, dense, opaque object (a "blackbody") will emit a continuous spectrum.
Student responses
Section 70158
(A) : 10 students
(B) : 14 students
(C) : 41 students
(D) : 4 students
"Difficulty level": 63%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55
20081017
Astronomy quiz question: absorption spectrum source
Astronomy 210 Quiz 4, Fall Semester 2008
Cuesta College, San Luis Obispo, CA
[4.0 points.] An absorption spectrum is caused by:
(A) the Doppler effect.
(B) hot, agitated electrons and atoms.
(C) electrons moving to lower energy orbitals.
(D) blackbody radiation passing through diffuse, cool gas atoms.
Correct answer: (D)
The electrons in the atoms in a cool, diffuse gas will absorb select wavelengths from a continuous spectrum source.
Student responses
Section 70160
(A) : 1 student
(B) : 11 students
(C) : 6 students
(D) : 13 students
"Difficulty level": 80%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49
Cuesta College, San Luis Obispo, CA
[4.0 points.] An absorption spectrum is caused by:
(A) the Doppler effect.
(B) hot, agitated electrons and atoms.
(C) electrons moving to lower energy orbitals.
(D) blackbody radiation passing through diffuse, cool gas atoms.
Correct answer: (D)
The electrons in the atoms in a cool, diffuse gas will absorb select wavelengths from a continuous spectrum source.
Student responses
Section 70160
(A) : 1 student
(B) : 11 students
(C) : 6 students
(D) : 13 students
"Difficulty level": 80%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49
20080720
Accretion disk radiation
"Brewster Rockit: Space Guy!" by Tim RickardJuly 5, 2008
There would probably be x-rays rather than near-UV rays emitted from the accretion disk surrounding a black hole, or perhaps beta particles (whether electrons or positrons) from Hawking radiation, especially if the black hole was sufficiently small.
20080527
Physics clicker question: blackbody versus silverbody
Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.22
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] What should the outside of your jacket be like, in order to stay as warm as possible when hiking at night (in the dark)?
(A) Shiny, reflective.
(B) Black, matte.
(C) (It depends on how cold it is outside.)
(D) (It doesn't matter what type of jacket is worn outside in the dark.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 11 students
(B) : 5 students
(C) : 0 students
(D) : 15 students
(E) : 0 students
Correct answer: (A)
The rate of heat absorbed/emitted by an object depends on its emissivity: 1 for a perfect blackbody, and 0 for a perfect silverbody. While a blackbody will be an efficient absorber, it will also be a perfect emitter, which is desirable when cooling is an issue (e.g., car radiators, bottom tiles on the Space Shuttle), but at night, when heat loss by radiation needs to be minimized, a jacket approximating a silverbody would be better.
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.22
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] What should the outside of your jacket be like, in order to stay as warm as possible when hiking at night (in the dark)?
(A) Shiny, reflective.
(B) Black, matte.
(C) (It depends on how cold it is outside.)
(D) (It doesn't matter what type of jacket is worn outside in the dark.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 11 students
(B) : 5 students
(C) : 0 students
(D) : 15 students
(E) : 0 students
Correct answer: (A)
The rate of heat absorbed/emitted by an object depends on its emissivity: 1 for a perfect blackbody, and 0 for a perfect silverbody. While a blackbody will be an efficient absorber, it will also be a perfect emitter, which is desirable when cooling is an issue (e.g., car radiators, bottom tiles on the Space Shuttle), but at night, when heat loss by radiation needs to be minimized, a jacket approximating a silverbody would be better.
20080512
Astronomy quiz question: accretion disk blackbody radiation
Astronomy 10 Quiz 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q10.3
[3.0 points.] Which one of the following choices best explains how accretion disks emit intense ultraviolet, and/or x-ray blackbody radiation?
(A) Heat generated from friction.
(B) Electrons jump down to lower orbits.
(C) Electrons flip their spins.
(D) Curvature of spacetime.
(E) Hydrogen fuses into helium.
Correct answer: (A)
A companion star of a compact object (white dwarf, neutron star, or black hole) may be close enough such that it will overflow its Roche lobe when it becomes a giant or superigant, thus transferring hydrogen to the compact object. This infalling hydrogen collects into an accretion disk surrounding the compact object, and due to Kepler's third law, the outer part of the disk orbits slower than the inner part of the disk. Due to the density of the disk, the difference in speeds between adjacent parts causes friction, producing enough heat for the disk to become incandescent, thus emitting blackbody radiation.
Student responses
Section 5166
(A) : 9 students
(B) : 17 students
(C) : 2 students
(D) : 3 students
(E) : 5 students
Previous post:
Astronomy in-class activity: compact objects with companion stars.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q10.3
[3.0 points.] Which one of the following choices best explains how accretion disks emit intense ultraviolet, and/or x-ray blackbody radiation?
(A) Heat generated from friction.
(B) Electrons jump down to lower orbits.
(C) Electrons flip their spins.
(D) Curvature of spacetime.
(E) Hydrogen fuses into helium.
Correct answer: (A)
A companion star of a compact object (white dwarf, neutron star, or black hole) may be close enough such that it will overflow its Roche lobe when it becomes a giant or superigant, thus transferring hydrogen to the compact object. This infalling hydrogen collects into an accretion disk surrounding the compact object, and due to Kepler's third law, the outer part of the disk orbits slower than the inner part of the disk. Due to the density of the disk, the difference in speeds between adjacent parts causes friction, producing enough heat for the disk to become incandescent, thus emitting blackbody radiation.
Student responses
Section 5166
(A) : 9 students
(B) : 17 students
(C) : 2 students
(D) : 3 students
(E) : 5 students
Previous post:
Astronomy in-class activity: compact objects with companion stars.
20080510
Astronomy quiz question: mass transfer in close-pair binaries
Astronomy 10 Quiz 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q10.2
[3.0 points.] Which one of the following choices best explains why the Roche lobes of two stars in a close-pair (mass-exchanging) binary system get smaller as they begin to orbit closer to each other?
(A) Gravitational forces get weaker.
(B) Centrifugal forces get stronger.
(C) Degeneracy pressure increases.
(D) Hydrogen is transferred slowly.
(E) Repeated nova explosions disrupts hydrogen transfer.
Correct answer: (B)
Due to conservation of angular momentum, the orbital speeds of the stars will increase as their separation distance decreases (as they would during hydrogen transfer from a more massive star to a less massive star). This will increase the centrifugal forces exerted on them, decreasing the size of their Roche lobes.
Student responses
Section 5166
(A) : 5 students
(B) : 29 students
(C) : 4 students
(D) : 7 students
(E) : 2 students
Related post:
Astronomy in-class activity: mass transfer in close-pair binaries.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q10.2
[3.0 points.] Which one of the following choices best explains why the Roche lobes of two stars in a close-pair (mass-exchanging) binary system get smaller as they begin to orbit closer to each other?
(A) Gravitational forces get weaker.
(B) Centrifugal forces get stronger.
(C) Degeneracy pressure increases.
(D) Hydrogen is transferred slowly.
(E) Repeated nova explosions disrupts hydrogen transfer.
Correct answer: (B)
Due to conservation of angular momentum, the orbital speeds of the stars will increase as their separation distance decreases (as they would during hydrogen transfer from a more massive star to a less massive star). This will increase the centrifugal forces exerted on them, decreasing the size of their Roche lobes.
Student responses
Section 5166
(A) : 5 students
(B) : 29 students
(C) : 4 students
(D) : 7 students
(E) : 2 students
Related post:
Astronomy in-class activity: mass transfer in close-pair binaries.
20080417
Astronomy clicker question: main sequence to giant/supergiant evolution
Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.1
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] According to the Stefan-Boltzmann law, how does the luminosity of a medium mass or massive main sequence star change as its outer layers expand and cool off, as it becomes a giant or supergiant?
(A) It becomes dimmer.
(B) It remains the same.
(C) It becomes brighter.
(D) (Any of the above (A)-(C) choices, depending on how old the star is.)
Correct answer: (B)
Student responses
Section 4160
(A) : 10 students
(B) : 14 students
(C) : 6 students
(D) : 2 students
Section 5166
(A) : 26 students
(B) : 5 students
(C) : 20 students
(D) : 3 students
According to the Stefan-Boltzmann law, the luminosity of a star is proportional to its size (its surface area) and the fourth power of its temperature. As a medium-mass or massive main sequence star becomes a giant or supergiant, its outer layers expand and cool. Thus the size increases while the temperature decreases, resulting in approximately the same luminosity as it makes a horizontal track to the right across a Hertzsprung-Russell diagram.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.1
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] According to the Stefan-Boltzmann law, how does the luminosity of a medium mass or massive main sequence star change as its outer layers expand and cool off, as it becomes a giant or supergiant?
(A) It becomes dimmer.
(B) It remains the same.
(C) It becomes brighter.
(D) (Any of the above (A)-(C) choices, depending on how old the star is.)
Correct answer: (B)
Student responses
Section 4160
(A) : 10 students
(B) : 14 students
(C) : 6 students
(D) : 2 students
Section 5166
(A) : 26 students
(B) : 5 students
(C) : 20 students
(D) : 3 students
According to the Stefan-Boltzmann law, the luminosity of a star is proportional to its size (its surface area) and the fourth power of its temperature. As a medium-mass or massive main sequence star becomes a giant or supergiant, its outer layers expand and cool. Thus the size increases while the temperature decreases, resulting in approximately the same luminosity as it makes a horizontal track to the right across a Hertzsprung-Russell diagram.
20071214
Hot coffee
"Any Tool (That's Some Powerful Hot Coffee!)," by MissChiefWorth1000.com
More Power 7 contest
"Caution: the coffee you are about to drink may be very hot."
20071109
Astronomy quiz question: applying the Stefan-Boltzmann law
Astronomy 10 Quiz 8, Fall Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[Version 1]
[3.0 points.] Consider two stars with the same luminosity. Which one of the following choices best describes the star that is larger in size?
(A) The star with the higher surface temperature.
(B) The star with the lower surface temperature.
(C) The star with the brighter apparent magnitude.
(D) The star with the dimmer apparent magnitude.
(E) (None of the above choices (A)-(D), as these two stars must have the same size.)
Correct answer: (B)
The Stefan-Boltzmann law states that luminosity is proportional to size and (temperature)^4. For two stars with the same luminosity, the larger size star must have a lower surface temperature.
Student responses
Section 0135
(A) : 7 students
(B) : 17 students
(C) : 3 students
(D) : 2 students
(E) : 0 students
[Version 2]
[3.0 points.] Consider two stars with the same size. Which one of the following choices best describes the star that has the higher surface temperature?
(A) The star with the brighter apparent magnitude.
(B) The star with the dimmer apparent magnitude.
(C) The star with the brighter luminosity.
(D) The star with the dimmer luminosity.
(E) (None of the above choices (A)-(D), as these two stars must have the same surface temperature.)
Correct answer: (C)
The Stefan-Boltzmann law states that luminosity is proportional to size and (temperature)^4. For two stars of the same size, the brighter luminosity star must have the higher surface temperature.
Student responses
Section 1073
(A) : 6 students
(B) : 1 student
(C) : 31 students
(D) : 3 students
(E) : 1 student
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[Version 1]
[3.0 points.] Consider two stars with the same luminosity. Which one of the following choices best describes the star that is larger in size?
(A) The star with the higher surface temperature.
(B) The star with the lower surface temperature.
(C) The star with the brighter apparent magnitude.
(D) The star with the dimmer apparent magnitude.
(E) (None of the above choices (A)-(D), as these two stars must have the same size.)
Correct answer: (B)
The Stefan-Boltzmann law states that luminosity is proportional to size and (temperature)^4. For two stars with the same luminosity, the larger size star must have a lower surface temperature.
Student responses
Section 0135
(A) : 7 students
(B) : 17 students
(C) : 3 students
(D) : 2 students
(E) : 0 students
[Version 2]
[3.0 points.] Consider two stars with the same size. Which one of the following choices best describes the star that has the higher surface temperature?
(A) The star with the brighter apparent magnitude.
(B) The star with the dimmer apparent magnitude.
(C) The star with the brighter luminosity.
(D) The star with the dimmer luminosity.
(E) (None of the above choices (A)-(D), as these two stars must have the same surface temperature.)
Correct answer: (C)
The Stefan-Boltzmann law states that luminosity is proportional to size and (temperature)^4. For two stars of the same size, the brighter luminosity star must have the higher surface temperature.
Student responses
Section 1073
(A) : 6 students
(B) : 1 student
(C) : 31 students
(D) : 3 students
(E) : 1 student
20070717
Astronomy clicker question: the Stefan-Boltzmann law
Astronomy 10, Summer Session 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the beginning of their learning cycle:
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: not revealed yet (see discussion).
This is the follow-up question after a short lecture (20 minutes) and an in-class activity (20 minutes) on how Wien's law and the Stefan-Boltzmann law describe blackbody radiation. Initial responses below:
Student responses
Section 8027
(A) : 3 students
(B) : 0 students
(C) : 3 students
(D) : 7 students
A leading question for the students: "Which star is hotter, and why?" Some students will have already realized that because these two stars have the same color, then they must be at the same temperature (application of Wien's law), and the class discusses why this must be the case. The same question is asked again, after the students collectively come to realization that both responses (C) and (D) cannot be true.
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: (A)
Student responses
Section 8027
(A) : 12 students
(B) : 1 student
(C) : 0 students
(D) : 0 students
The Stefan-Boltzmann law states that luminosity is proportional to size (that is, surface area) and temperature (T^4). Since they are the same temperature, then the less luminous star must be smaller in size than the more luminous star, which is larger in size.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the beginning of their learning cycle:
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: not revealed yet (see discussion).
This is the follow-up question after a short lecture (20 minutes) and an in-class activity (20 minutes) on how Wien's law and the Stefan-Boltzmann law describe blackbody radiation. Initial responses below:
Student responses
Section 8027
(A) : 3 students
(B) : 0 students
(C) : 3 students
(D) : 7 students
A leading question for the students: "Which star is hotter, and why?" Some students will have already realized that because these two stars have the same color, then they must be at the same temperature (application of Wien's law), and the class discusses why this must be the case. The same question is asked again, after the students collectively come to realization that both responses (C) and (D) cannot be true.
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: (A)
Student responses
Section 8027
(A) : 12 students
(B) : 1 student
(C) : 0 students
(D) : 0 students
The Stefan-Boltzmann law states that luminosity is proportional to size (that is, surface area) and temperature (T^4). Since they are the same temperature, then the less luminous star must be smaller in size than the more luminous star, which is larger in size.
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