Astronomy midterm question: comparing different temperature, same size stars

Astronomy 210 Midterm 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

lilred309012004: What can we expect...when we look at stars [the same distance from Earth] with different surface temperatures but the same size?
abhi: [T]he star will be much brighter if it is...hot [and] blue...and much fainter and redder if it is...cool...

Decide whether or not if this answer is correct, and how you know this. Explain using Wien's law, the Stefan-Boltzmann law and/or an H-R diagram.

*Source: http://answers.yahoo.com/question/index?qid=20091012033431AAWHcdW.

Solution and grading rubric:

• p = 20/20:
  Correct. Uses Wien's law, the Stefan-Boltzmann law and/or interprets H-R diagram to show that a hotter, bluer star will be more luminous than a cooler, redder star.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use Wien's law, H-R diagram and/or the Stefan-Boltzman law.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion not based on Wien's law, H-R diagram and/or the Stefan-Boltzman law.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm02sA4r
p: 24 students
r: 6 students
t: 6 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 0308):
Another sample "p" response (from student 4444):
A sample "v" response (from student 5476), misapplying Wien's law:
Yet another sample "v" response (from student 1033), misapplying the Stefan-Boltzmann law:

Astronomy midterm question: low-mass stars in young star cluster?

Astronomy 210 Midterm 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

Eli: In a...young star cluster, if the...massive stars are swelling up into [supergiants], the low mass stars [are...]?
Twizard113: ...[Continuing] to shine as...main sequence stars...

Decide whether or not if this answer is correct, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20081119115729AA2IQ67.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that massive stars evolve faster than low-mass stars, such that by the time massive stars have already gone through their protostar to main sequence to supergiant phases, medium-mass stars are now on the main sequence, but low mass stars are still protostars, and have not yet become red dwarfs on the main sequence.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. As (p), but claims low mass stars would be on main sequence.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least understands correlation between mass and main sequence lifetime.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion other than that of the properties and evolution of stars.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm02sA4r
p: 13 students
r: 6 students
t: 13 students
v: 3 students
x: 3 students
y: 0 students
z: 0 students

A sample "p" response (from student 4392), showing the star cluster on an H-R diagram:
Another sample "p" response (from student 1014), discussing the relative evolution rates of massive vs. low-mass stars:
Yet another sample "p" response (from student 5040), discussing the "House Party" analogy of stellar evolution:

Astronomy midterm question: star cluster with type II supernovae?

Astronomy 210 Midterm 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

Fey Lin: If you were looking for massive-star supernovae, in which type of star cluster would you look?
ronwizfr: [A] very young cluster [instead of a very old cluster]...

Decide whether or not if this answer is correct, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20100216080213AAO5SDI.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that massive stars evolve faster than low-mass stars, such that a younger star cluster will have massive stars that will have already gone through their protostar to main sequence to supergiant phases, in order to soon explode as (type II) supernovae.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least understands correlation between mass and main sequence lifetime.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion other than that of the properties and evolution of stars.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm02n4Rg
p: 20 students
r: 1 students
t: 3 students
v: 9 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7538), showing the evolution of the star cluster on an H-R diagram:
Another sample "p" response (from student 5213), discussing the relative evolution rates of massive vs. medium mass stars:
Yet another sample "p" response (from student 2393), using the "House Party" analogy of stellar evolution rates:
A sample "v" response (from student 1313):

Astronomy midterm question: new stars from type II/type Ia supernova remnants?

Astronomy 210 Midterm 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

[Version 1]
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

owen m: [How c]an another [star] form after a [type II] supernova?
Stom: [W]hen a star...goes [type II] supernova, it blasts a...lot of unused hydrogen out into space...and when there is enough hydrogen pulled together and the gravity gets strong enough the new star burst[s] [into] life...

Discuss why this answer is correct, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20090914144056AA43heK.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that type II supernova remnants are hydrogen rich, discussing hydrogen line spectra evidence and/or that the outer layers of a supergiant are uninvolved in core/shell fusion, and thus are primarily hydrogen, from which a subsequent star can form, and/or may discuss new star formation triggered by type II supernova shockwaves.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Does not directly address why discussion board answer is correct, but at least demonstrates understanding of type II supernova process.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on type Ia supernova or other types of stars/supernovae, or focuses on star formation only instead of also discussing hydrogen contribution from type II supernovae.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. May describe/restate discussion board answer without substantive explanation involving properties and evolution of stars as to why it is correct.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm02sA4r
p: 10 students
r: 5 students
t: 12 students
v: 7 students
x: 4 students
y: 0 students
z: 0 students

A sample "p" response (from student 2448):

[Version 2]
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

owen m: [How c]an another [star] form after a [type Ia] supernova?
Stom: [W]hen a star...goes [type Ia] supernova, it blasts a...lot of unused hydrogen out into space...and when there is enough hydrogen pulled together and the gravity gets strong enough the new star burst[s] [into] life...

Discuss why this answer is incorrect, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20090914144056AA43heK.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that type Ia supernova remnants are hydrogen poor, discussing hydrogen line spectra evidence and/or that the carbon-oxygen white dwarf steals hydrogen from a companion star, and fuses these to heavier elements when exploding, leaving very little (if any) hydrogen from which a subsequent star can form.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Does not directly address why discussion board answer is incorrect, but at least demonstrates understanding of type Ia supernova process.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on type Ia supernova or other types of stars/supernovae, or focuses on star formation only instead of also discussing hydrogen contribution from type II supernovae.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. ay describe/restate discussion board answer without substantive explanation involving properties and evolution of stars as to why it is incorrect.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm02n4Rg
p: 8 students
r: 0 students
t: 11 students
v: 11 students
x: 3 students
y: 0 students
z: 0 students

A sample "p" response (from student 7538):

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2012
Cuesta College, San Luis Obispo, CA

Section 30882, version 1
Exam code: quiz06LR1r

Section 30882 results
Quiz 6 results (max score = 30):

0- 6 :
7-12 :	** [low = 12]
13-18 :	*****
19-24 :	************* [mean = 22.0 +/- 4.9]
25-30 :	****** [high = 30]

Livetweets: SCAAPT spring 2012 meeting

American Association of Physics Teachers, Southern California Section
Spring 2012 meeting
http://www.scaapt.org/meetings/2012mtg1spr/program.htm

Scraped archive of publicly visible live tweets, using #scaapt2012 and #scaaptsp12 hashtags.

Winner of #scaaptsp12 order-of-magnitude question: how many years until Earth population is standing room only? 650 years (10^3 years).
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): Sign up for Southern California Regional Teaching Exchange astronomy101.jpl.nasa.gov/workshopdetail… May 5, 2012 #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): Plugging Center for Astronomy Education website astronomy101.jpl.nasa.gov #astro101 #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): Use "confront-elicit-resolve" teaching strategy to address#astro101 student misconceptions. #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): pre- to post- #astro101 normalized learning gains above 0.60 = "unobtanium." #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): active learning strategies in #astro101 help everyone, but...implementation matters! #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Rica French (Mira Costa College): due to vast number of students, when you teach introductory astronomy, you teach the world. #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Ertan Salik (Cal Poly Pomona) shared poems from Nin Andrews' "Dear Professor, Do You Live In A Vacuum?" books.google.com/books?id=YkBON… #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Michael Anderson (UCSD): students valued points from peer votes for best #physics101 video as much as instructor grade points #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Michael Anderson (UCSD): each student in group of 3-4 must be visible/audible, explain concept and demonstrate in 4-9 min video #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Michael Anderson (UCSD): students engaged by working on videos to present, explain #physics101 concepts #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Vivek Sharma (UCSD): 2012 expected to be momentous year, find Higgs boson w/5*sigma significance, or existence ruled out #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Vivek Sharma (UCSD): Higgs boson been discovered? "Not yet! We want to be careful." CMS, ATLAS each 5*sigma evidence required #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Vivek Sharma (UCSD): Particle accelerator: charges, battery, magnet...you may have had one before replacing w/flat-screen LCD TV #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Vivek Sharma (UCSD): Standard Model has no mechanism for mass unless scalar "Higgs" field postulated #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Vivek Sharma (UCSD): imagine massless quarks, leptons--p, n has mass due to quark confinement energy, but electrons massless #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

This would truly be one tough game of Boggle to play (standard model of elementary particles) upload.wikimedia.org/wikipedia/comm… #scaaptsp12 #scichat
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Tim Heumier (Azusa Pacific University) radioactive decay dice: "plot" of activity per time. #scaaptsp12 #moredataneeded twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Tim Heumier (Azusa Pacific University) radioactive decay dice: wooden cubes, one side spray-painted black. #scaaptsp12 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Tim Heumier (Azusa Pacific University) : Mars at superior conjunction as big as full moon misconception: "full of bogosity." #scaaptsp12
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Robert Gill (CSU-SM) co-opted one of my #astro101 student wordles for #scaaptsp12 talk! flickr.com/photos/waiferx… #justsaying no CC-attribution?
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): common #phys101 student question on clicker (peer-instruction) points. #scaaptsp12 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Wow--Cal State San Marcos bottles its own spring water. #scaaptsp12 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Whoops--check #scaapt2012 hashtags from earlier this morning for #scaaptsp12 posts.
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): Someone always better than you at giving the "best" lecture, why should that be your goal? #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

"sitting at the back of a lecture is already distance learning" #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): technology should be driven by pedagogical goals #scaapt2012 #tongueincheek twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): student whiteboards ("always boot up"), posted to flickr.com #scaapt2012 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Ss were more interested in correcting their work, Ss were more active in the class, awesome! #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

and taking pictures and posting them on flicker for viewing later was better #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

interesting, they found out the old fashioned whiteboards were better than tablets, 1/2 #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): whiteboards vs. TabletPCs for student presentations #scaapt2012 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): #phys101 peer-instruction ("clicker") question example. #scaapt2012 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM) used my version of flashcards in their slide (upper left). #scaapt2012 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Charles De Leone, Ed Price (CSU-SM): easy vs. hard pedagogical goals. #scaapt2012 twitter.com/Patrick_M_Len/…
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Jeff Phillips (SCAAPT President): Charles De Leone, Ed Price (CSU-SM) "youngest, and most handsomest physics department." #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

PhysTEC is yet another Physics teacher education coalition. .why aren't all this things more centralized? #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

Chris Abel (SoCal Edison): no Cerenkov radiation visible at San Onofre, not typical for U.S. facilities. #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

@RuttigerSD You know that person in front row tweeting during your presentation? I want you to be that person. #scaapt2012 #livetweet
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Chris Abel (SoCal Edison) personally respects people against nuclear power, just want them to be informed about their opinions #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Chris Abel (SoCal Edison) 30' tsunami wall, withstand 19'-22' worse case, all-time historical max. tsunami was 2' at San Onofre. #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Chris Abel (SoCal Edison): 19% of Southern California electricity from San Onofre Nuclear Power Plant. #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

proposal help HS teachers build their own HS clusters and they get some CPU time, we get increased computer skills. #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

This talk is mainly for high volume data analysis.. interesting, but not so useful for me in HS physics.#SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

The talks here just reitterate how every physics teacher should participate in #globalphysicsdepartment #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

@RuttigerSD This is what live-tweeting is all about. All the cool instructors are doing it. #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

making a graph that conveys what you want to convey is an art form #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

John Price (CSU-DH): "Physics is hard to do _without_ the aid of computers," includes disseminating results as well. #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

how to build your own computer cluster andwhy you want to #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

Greg Severn (USD): "Failure is overrated." #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Greg Severn (USD): Einstein/de-Haas experiment "isn't the most famous experiment that didn't work," cf. Stern-Gerlach #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

Greg Severn (USD) explaining foibles of Einstein/de-Haas experiment torquing iron rod with external magnetic field #scaapt2012
— Patrick M. Len (@Patrick_M_Len) April 21, 2012

What does it mean to do an experiment well? #SCAAPTsp12
— Chija Bauer (@bauerphysics) April 21, 2012

Overheard: whiteboard penmanship

Physics 205B, spring semester 2012
Cuesta College, San Luis Obispo, CA

(Overheard after the end of algebra-based introductory physics lecture on Faraday's law/Lenz's law.)

Student: "I have to ask, did you ever take a course in whiteboard writing?"

Instructor: (Beat.) "Uh, what do you mean by 'whiteboard writing?'"

Student: "You know, learning how to write neatly on a whiteboard. You have better handwriting on the whiteboards than me, or teachers in my other courses."

Astronomy quiz archive: Milky Way, cosmology

Astronomy 210 Quiz 6, spring semester 2012
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz06niLl
Section 30674

0- 8.0 :
8.5-16.0 :	*** [low = 10.5]
16.5-24.0 :	*************
24.5-32.0 :	************* [mean = 24.4 +/- 6.5]
32.5-40.0 :	**** [high = 36.5]

Section 30676, version 1
Exam code: quiz06suE7
Section 30676

0- 8.0 :	**** [low = 7.0]
8.5-16.0 :	******
16.5-24.0 :	************** [mean = 19.8 +/- 8.1]
24.5-32.0 :	*********
32.5-40.0 :	** [high = 40.0]

Physics quiz archive: capacitors, circuits (2)

Physics 205B Quiz 5, spring semester 2012
Cuesta College, San Luis Obispo, CA

Section 30882, version 1
Exam code: quiz05Vo7x

Section 30882 results
Quiz 5 results (max score = 30):

0- 6 :	*** [low = 6]
7-12 :	*******
13-18 :	******** [mean = 16.2 +/- 6.7]
19-24 :	*****
25-30 :	*** [high = 30]

Physics quiz quesiton: light bulb power dissipation in circuit

Physics 205B Quiz 5, spring semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.65(e)

An ideal 12 V emf source is connected to two 1.6 Ω resistors, a 7.0 Ω resistor, and two ideal voltmeters, as shown at right. Which light bulb is brighter?
(A) Bulb 1.
(B) Bulb 2.
(C) (There is a tie, but both bulbs are completely dead.)
(D) (There is a tie, with both bulbs lit.)

Correct answer: (D)

The two light bulbs are in series with each other, such that there is the same amount of current I passing through both. (The voltmeters are ideal and have infinite resistance, such that no current will be diverted away from bulb 2). Thus the power dissipated by the bulbs will be the same:

P = I²*R.

Section 30882
Exam code: quiz05Vo7x
(A) : 12 students
(B) : 1 student
(C) : 1 student
(D) : 12 students

Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58