P-dog's blog: boring but important: 201005

20100529

Cuesta College North County campus star party

100415-1150373
http://www.flickr.com/photos/waiferx/4620396177/
Originally uploaded by Waifer X

Waxing crescent moon, April 15, 2010, photographed with a handheld Panasonic Lumix DMC-LZ8 camera through a Orion 10" reflector at Cuesta College North County campus, Paso Robles, CA. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

100415-1150381
http://www.flickr.com/photos/waiferx/4621009196/
Originally uploaded by Waifer X

Venus and waxing crescent moon, April 15, 2010, photographed with a Panasonic Lumix DMC-LZ8 camera set on long-exposure mode at Cuesta College North County campus, Paso Robles, CA. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

Sights seen:
Waxing crescent moon
Venus
Saturn

20100527

Astronomy current events question: M81 halo

Astronomy 210L, Spring Semester 2010
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!)

Kelly Beatty, "A New Take on M81's Halo," May 3, 2010
http://www.skyandtelescope.com/news/92734814.html

Researchers using data from Japan's Subaru telescope have determined that the halo of spiral galaxy M81 __________ than the halo of the Milky Way.
(A) is mainly composed of antimatter.
(B) contains much more dark matter.
(C) is more abundant in heavy elements.
(D) is much smaller.
(E) has a greater redshift.

Correct answer: (B)

Student responses
Section 30682
(A) : 0 students
(B) : 4 students
(C) : 5 students
(D) : 0 students
(E) : 1 student

20100526

Astronomy current events question: galactic bubble RCW 120

Astronomy.com editors, "Herschel Reveals the Hidden Side of Star Birth," May 6, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9829

The European Space Agency's Herschel infrared space observatory has revealed __________ in the galactic bubble RCW 120.
(A) the formation of a black hole.
(B) a star that may become one of the Milky Way's biggest.
(C) a wormhole candidate.
(D) the source of dark energy.
(E) carbon-based organic compounds.

Correct answer: (B)

Student responses
Section 30682
(A) : 1 student
(B) : 6 students
(C) : 1 student
(D) : 2 students
(E) : 1 student

20100518

Physics midterm problem: unknown voltmeter reading

Physics 205B Midterm 2, spring semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.74

An ideal 15 V emf source is connected to ideal resistors and an ideal voltmeter, as shown at right. What is the reading of the voltmeter? Show your work and explain your reasoning using the properties of currents and potential differences, and Kirchhoff's rules and Ohm's law.

Solution and grading rubric:

p:
Correct. From application of Kirchhoff's loop rule, voltmeter reading would be either 15 V - (6.0 Ω)·I₆, or (1.0 Ω)·I₁, or (5.0 Ω)·I₅, with I₆, I₁, and I₅ being the currents going through the 6.0 Ω resistor, 1.0 Ω light bulb, and 5.0 Ω resistor, respectively. Correctly finds one (or all) of the currents in this circuit by use of equivalent resistance, Ohm's law, and Kirchhoff's junction rule, and uses current(s) to determine the voltmeter reading.
r:
Nearly correct, but includes minor math errors.
t:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least finds equivalent resistance of circuit, and main current I₆ = 2.2 A.
v:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
x:
Implementation of ideas, but credit given for effort rather than merit.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 31988
p: 4 students
r: 2 students
t: 3 students
v: 3 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 1230):

20100515

Astronomy midterm question: Doppler redshifts and the expanding universe

Astronomy 210 Midterm 2, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Doppler shifts of galaxies is evidence that the universe is expanding. Explain what these Doppler shifts are, and how they are used to support the theory of an expanding universe.

Solution and grading rubric:

p = 20/20:
Correct. Explains Doppler shifts show that light from galaxies are redshifted (stretched out to longer wavelength values) proportional to their distances, and thus indicate the universe is expanding (Hubble's law).
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. Description of Doppler shifts missing/problematic, but adequate discussion of Hubble's law (or at least the general implication of an expanding universe based on galaxies receding), or vice versa.
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.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 30674
p: 14 students
r: 4 students
t: 23 students
v: 1 student
x: 0 students
y: 2 students
z: 0 students

Section 30676
p: 16 students
r: 7 students
t: 32 students
v: 19 students
x: 1 student
y: 0 students
z: 1 student

A sample "p" response (from student 4747):

Another sample "p" response (from student 4733):

A refreshingly honest "y" response (from student 7272):

20100514

Astronomy midterm question: possible/impossible star cluster H-R diagrams

Astronomy 210 Midterm 2, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

[20 points.] Shown at right could be an H-R diagram of a star cluster, where all of these stars would have the same age. Discuss whether or not this H-R diagram is possible for a star cluster, and explain why, using the properties of stars and evolution times.

Solution and grading rubric:

p = 20/20:
Correct. Understands that massive stars evolve faster than low-mass stars, such that massive stars reach the upper left of the main sequence first, spend the least amount of time there, and leave well before low-mass stars become main-sequence stars. Therefore the H-R diagram is not possible for a star cluster where the stars would have the same age.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Argument based on interpreting low-mass stars lying just off of the main sequence line as leaving the main sequence, which is yet to be observed given the age of the universe (while ignoring the presence of massive stars on the main sequence).
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least understands how massive and low-mass stars evolve at different rates to get to (and leave) the main sequence.
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.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 30674
p: 34 students
r: 1 student
t: 5 students
v: 3 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 1802):

Another sample "p" response (from student 0310):

Yet another sample "p" response (from student 0299), mentioning the "house party" analogy discussed in class:

A sample "v" response (from student 2569), noticing an apparent lack of medium-mass stars on the main sequence:

[Version 2]

p = 20/20:
Correct. Understands that massive stars evolve faster than low-mass stars, such that massive stars reach the upper left of the main sequence first, spend the least amount of time there, and leave well before low-mass stars become main-sequence stars. Therefore the H-R diagram is possible for a star cluster where the stars would have the same (old) age.
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 how massive and low-mass stars evolve at different rates to get to (and leave) the main sequence.
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. Conclusion without substantive argument.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 30676
p: 35 students
r: 5 students
t: 4 students
v: 25 students
x: 7 students
y: 0 students
z: 0 students

A sample "p" response (from student 0264), also describing the cause of different evolution rates for massive and low-mass stars:

A sample "p" response (from student 8282), appealing to the "house party" analogy:

A sample "v" response (from student 1001), with a whimsical threat:

A brutally self-honest "x" response (from student ), in manga form:

20100513

Astronomy midterm question: Polaris vs. Vega; Deneb vs. Polaris

Astronomy 210 Midterm 2, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

[20 points.] Consider the stars Polaris and Vega. Polaris is hotter, but its luminosity is dimmer; while Vega is cooler, but its luminosity is brighter. Discuss if it is possible for these stars to be the same size; if this is not possible, then determine which star (Polaris or Vega) must be larger. Support your answer using Wien's law and/or the Stefan-Boltzmann law.

Solution and grading rubric:

p = 20/20:
Correct. Discusses how the Stefan-Boltzmann law (luminosity (brightness) proportional to size * (Temperature)^4) explains that the cooler of the two stars must be much larger in order to have a greater luminosity than the hotter star. Or may plot points on an H-R diagram, and shows that these two stars cannot lie along an equal radius diagonal.
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 recognizes how the Stefan-Boltzmann law is applicable, but argument is garbled (e.g., has stars being the same size as possible).
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Involves other factors such as distance, fusion rates, dimming by the interstellar medium, etc., typically confusing luminosity with apparent magnitude rather than absolute visual magnitude.
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 30674
p: 27 students
r: 2 students
t: 11 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1415):

Another sample "p" response (from student 5239), referring to an H-R diagram:

Another sample "p" response (from student 6042), using a table of Stefan-Boltzmann law entries:

[Version 2]

[20 points.] Consider the stars Deneb and Polaris. Deneb is hotter and its luminosity is brighter; while Polaris is cooler and its luminosity is dimmer. Decide if it is possible for these stars to be the same size; if this is not possible, then determine which star (Deneb or Polaris) must be larger. Support your answer using Wien's law and/or the Stefan-Boltzmann law.

Solution and grading rubric:

p = 20/20:
Correct. Discusses how the Stefan-Boltzmann law (luminosity (brightness) proportional to size * (Temperature)^4) explains that the cooler of the two stars must be much larger in order to have a greater luminosity than the hotter star. Or may plot points on an H-R diagram, and shows that these two stars may lie along an equal radius diagonal.
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 recognizes how the Stefan-Boltzmann law is applicable, but argument is garbled (e.g., has stars being the same size as possible).
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Involves other factors such as distance, fusion rates, dimming by the interstellar medium, etc., typically confusing luminosity with apparent magnitude rather than absolute visual magnitude.
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 30676
p: 38 students
r: 1 student
t: 27 students
v: 8 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 9033):

A sample "p" response (from student 1007):

20100512

Astronomy current events question: Mars rover 3D camera

Tim Hornyak, "James Cameron Building 3D Cam for Mars Rover," April 29, 2010
http://news.cnet.com/8301-17938_105-20003827-1.html

James Cameron, Academy Award winning director of Avatar, is working with NASA to develop:
(A) remote controlled robots for dangerous spacewalk missions.
(B) a documentary on living aboard the International Space Station.
(C) virtual reality technology to train astronauts.
(D) a 3D camera for the next Mars rover.
(E) computer animations of lifeforms that may exist on exoplanets.

Correct answer: (D)

Student responses
Sections 30678, 30679, 30680
(A) : 0 students
(B) : 5 students
(C) : 3 students
(D) : 45 students
(E) : 3 students

20100511

Astronomy current events question: Lunkhod 1 retroreflector

Astronomy.com editors, "Lunokhod 1 Retroreflector Found," April 27, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9804

NASA has rediscovered the positions of the Russian Lunakhod 1 retroreflector on the surface of the moon. This retroreflector will be used to study:
(A) how slowly the moon is moving away from Earth.
(B) secrets of early Russian space technology.
(C) prolonged effects of solar wind on metal alloys.
(D) the very sparse atmosphere of the moon.
(E) the slow formation of ice on lunar surfaces.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 32 students
(B) : 0 students
(C) : 13 students
(D) : 4 students
(E) : 6 students

20100510

Astronomy current events question: asteroid 24 Themis

Astronomy.com editors, "Ice Lurks in Asteroid's Cold Heart," April 29, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9811

Observations from the NASA Infrared Telescope Facility have revealed the presence of __________ on asteroid 24 Themis.
(A) radioactive elements.
(B) dark matter.
(C) water ice and carbon-based organic compounds.
(D) fragments of the large impact that created Earth's moon.
(E) solar neutrinos.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 4 students
(B) : 3 students
(C) : 45 students
(D) : 3 students
(E) : 0 students

20100509

Astronomy current events question: return of Neptune

Kelly Beatty, "The Return of Neptune," April 16, 2010
http://www.skyandtelescope.com/news/91136009.html

Next year, Neptune is expected to:
(A) eclipse Jupiter and Uranus.
(B) be visible to the naked eye.
(C) cross orbits with, and be closer than Uranus to the sun.
(D) be renamed after its original discoverers.
(E) complete its first orbit since its discovery.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 2 students
(B) : 5 students
(C) : 0 students
(D) : 2 students
(E) : 44 students

20100508

Astronomy current events question: planet GJ 436B

Astronomy.com editors, "Distant Planet Missing Common Ingredient," April 22, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9791

The NASA Spitzer Space Telescope has discovered that the planet GJ 436B, about the size of Neptune, is missing __________, an ingredient common to many solar system planets.
(A) oxygen.
(B) water vapor.
(C) nitrogen.
(D) carbon dioxide.
(E) methane.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 1 student
(B) : 1 student
(C) : 6 students
(D) : 4 students
(E) : 41 students

20100507

Astronomy current events question: LUCIFER camera/spectrograph

Astronomy.com editors, "LUCIFER Allows Astronomers to Watch Stars Being Born," April 23, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9796

The new LUCIFER 1 camera/spectrograph for the Large Binocular Telescope (LBT) uses near-infrared light instead of visible light to observe star and planet formation, because near-infrared light is:
(A) more flexible than visible light.
(B) a particle, not a wave.
(C) slower than visible light.
(D) not affected by lookback time.
(E) not blocked by interstellar dust clouds.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 7 students
(B) : 1 student
(C) : 0 students
(D) : 1 student
(E) : 17 students

20100506

Astronomy current events question: VISTA camera/spectrograph

Astronomy.com editors, "VISTA Captures Celestial Cat's Hidden Secrets," April 21, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9781

The new VISTA camera/spectrograph for the European Southern Observatory uses near-infrared light instead of visible light to observe star and planet formation, because near-infrared light is:
(A) more flexible than visible light.
(B) slower than visible light.
(C) not affected by lookback time.
(D) a particle, not a wave.
(E) not blocked by interstellar dust clouds.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 6 students
(B) : 0 students
(C) : 2 students
(D) : 0 students
(E) : 19 students

20100505

Astronomy current events question: lightning on Saturn

Astronomy.com editors, "NASA's Cassini Spacecraft Sees Lightning on Saturn," April 15, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9757

The NASA Cassini spacecraft has recently imaged the first movies of __________ on Saturn.
(A) methane cyclones.
(B) falling dry ice snow.
(C) new ring formation.
(D) a "Great White Spot."
(E) visible lightning flashes.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 0 students
(B) : 0 students
(C) : 2 students
(D) : 1 student
(E) : 26 students

20100504

Astronomy current events question: seasons on Triton

Astronomy.com editors, "Triton's Summer Sky of Methane and Carbon Monoxide," April 7, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9731

What is the evidence from the European Southern Observatory's Very Large Telescope that the atmosphere of Neptune's largest moon, Triton, changes with the seasons?
(A) Increasing amounts of gases.
(B) Shrinking polar caps.
(C) Changes in surface roughness.
(D) Shifting tectonic plates.
(E) Rising methane ocean levels.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 41 students
(B) : 2 students
(C) : 3 students
(D) : 3 students
(E) : 1 student

20100503

Astronomy current events question: Epsilon Aurigae eclipse

Astronomy.com editors, "Astronomers Capture Rare Stellar Eclipse in Opening Scene of Yearlong Show," April 8, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9734

Recent images of the star Epsilon Aurigae indicate that it is being eclipsed by an opaque disk surrounding a nearby:
(A) star.
(B) asteroid.
(C) black hole.
(D) planet.
(E) comet.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 41 students
(B) : 2 students
(C) : 3 students
(D) : 3 students
(E) : 1 student

20100502

Astronomy current events question: Venus alive?

Astronomy.com editors, "Venus Is Alive, Geologically Speaking," April 9, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9736

What is the evidence from the European Space Agency's Venus Express spacecraft that Venus may still be geologically active?
(A) Newly discovered impact craters.
(B) Rising volcanic peaks.
(C) Different compositions of certain lava flows.
(D) Gases released from fissures.
(E) Impact craters missing from earlier photos.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 1 student
(B) : 10 students
(C) : 28 students
(D) : 1 students
(E) : 21 students