Kudos: now I get Piet Hein

Poem displayed on the overhead digital projector during the final exam:

"The road to wisdom? -- Well, it's plain
and simple to express:
            Err
            and err
            and err again
            but less
            and less
            and less."
      --Piet Hein, "The Road to Wisdom," Grooks (1966)

"Now I Get It," by Student 5613
Physics 205B
May 2014
Cuesta College, San Luis Obispo, CA

Kudos: because of the way you instructed it

"Because of the Way You Instructed It," by Student 7810
Physics 205B
May 2014
Cuesta College, San Luis Obispo, CA

Physics quiz archive: radioactive decay, Feynman diagrams

Physics 205B Quiz 7, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz07bC4n



Sections 30882, 30883 results

0- 6 :
7-12 :	*** [low = 12]
13-18 :	****************
19-24 :	************ [mean = 20.4 +/- 5.4]
25-30 :	******* [high = 30]

Astronomy quiz archive: Milky Way, cosmology

Astronomy 210 Quiz 7, spring semester 2014
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz07nU7e


Section 30674

0- 8.0 :
8.5-16.0 :	*** [low = 15.0]
16.5-24.0 :	*************
24.5-32.0 :	****** [mean = 24.2 +/- 6.1]
32.5-40.0 :	**** [high = 36.0]

Section 30676, version 1
Exam code: quiz07s1Rp


Section 30676

0- 8.0 :
8.5-16.0 :	***** [low = 8.5]
16.5-24.0 :	***************** [mean = 22.2 +/- 6.6]
24.5-32.0 :	********
32.5-40.0 :	**** [high = 33.0]

Astronomy midterm question: Martian volcanoes reactivating?

Astronomy 210 Midterm 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was asked and answered:

py: What would happen if Mars' volcanoes became active again? Like if all of the sudden Olympus Mons just exploded and melted the ice caps? Would Mars' climate become more like Earth's?
Al: (a) It would be impossible for Mars' volcanoes to become active again, but (b) if they could become active, Mars' climate would then become more Earth-like.

Discuss why both these answers (a)-(b) are correct, and how you know this. Explain using the properties of greenhouse gases and geological activity.

[*] Adapted from https://answers.yahoo.com/question/index?qid=20110615233622AAjIa8s.

Solution and grading rubric:

• p = 20/20:
  Discusses why both statements are correct: (a) Mars' volcanic activity has ceased because there is no heat left in its small core, which caused it to cool off rapidly; and (b) if there was an increase in volcanic activity, outgassing and melting of polar ice caps would introduce more carbon dioxide and water vapor greenhouse gases, allowing Mars to retain more heat from the sun and increase its atmospheric temperatures.
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. One of two points (a)-(b) correct, other is problematic/incomplete.
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Both points (a)-(b) problematic/incomplete, or one point correct while other is missing.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least understands factors that contribute to (lack of) volcanic activity and greenhouse effect.
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discusses factors other than relevant to geological activity and greenhouse effect.
• y = 2/20:
  Irrelevant discussion/effectively blank.
• z = 0/20:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm02n4iL
p: 10 students
r: 6 students
t: 8 students
v: 2 students
x: 2 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm02sh7F
p: 18 students
r: 5 students
t: 12 students
v: 7 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 0123):
Another sample "p" response (from student 7342):
A sample "t" response (from student 1378), only discussing why Mars' volcanoes cannot erupt again:
Another sample "t" response (from student 6620), only discussing the effect of volcanic eruptions on Mars' climate:

Astronomy midterm question: cooler star more luminous than a hotter star?

Astronomy 210 Midterm 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was given the following answers:

CM: I keep thinking that a cooler star could be more luminous than a hotter star--is this true?
Okl: No, it cannot be true.
Do: There are situations in which this may be true.

Discuss why this answer is incorrect, and how you know this. Explain using Wien's law, the Stefan-Boltzmann law and/or an H-R diagram.

[*] Adapted from https://answers.yahoo.com/question/index?qid=20090316143453AAmTD1h.

Solution and grading rubric:

• p = 20/20:
  Uses Wien's law, the Stefan-Boltzmann law and/or interprets H-R diagram to show specifically how it is possible for a cooler star to be more luminous than a hotter star, provided that the cooler star is sufficiently larger than the hotter star.
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. As (p), but may instead demonstrate how a cooler star could be equally luminous as a hotter star.
• 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-Boltzmann 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-Boltzmann law.
• y = 2/20:
  Irrelevant discussion/effectively blank.
• z = 0/20:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm02n4iL
p: 22 students
r: 4 students
t: 1 student
v: 0 students
x: 1 student
y: 0 students
z: 0 students
z: 0 students

A sample "p" response (from student 0507) using an H-R diagram:
Another sample "p" response (from student 0794) using the "box model" of the Stefan-Boltzmann law:
Yet another sample "p" response (from student 3946) showing all the possible entries in the Stefan-Boltzmann "box model":

Astronomy midterm question: brighter, larger star is hotter?

Astronomy 210 Midterm 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was asked and answered:

qu: If you have two stars that are at equal distance, and one is brighter than the other, then the brighter one must be hotter if it is the larger one.

Discuss why this answer would not necessarily always be correct, and how you know this. Explain using Wien's law, the Stefan-Boltzmann law and/or an H-R diagram.

[*] answers.yahoo.com/question/index?qid=20140327175847AARrJhx.

Solution and grading rubric:

• p:
  Correct. Uses Wien's law, the Stefan-Boltzmann law and/or interprets H-R diagram to discuss how a brighter/larger star does not necessarily have to be hotter than a dimmer/smaller star, by comparing:

  • bright/larger/cooler vs. dim/smaller/hotter stars;
  • bright/larger/(same temperature) vs. dim/smaller/(same temperature) stars;

  or makes other comparisons between:

  • bright/smaller/hotter vs. dim/larger/cooler stars;
  • bright/(same size)/hotter vs. dim/(same size)/cooler stars.

• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Or as (p), but may instead compare:

  • (same brightness)/smaller/hotter vs. (same brightness)/larger/cooler stars;

  despite being given "one star is brighter than the other."
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
• v:
  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-Boltzmann law.
• x:
  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-Boltzmann law.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30676
Exam code: midterm02sh7F
p: 26 students
r: 4 students
t: 3 students
v: 8 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 0417) showing that the brighter, larger star could be cooler:
Another sample "p" response (from student 1000) showing that the brighter, hotter star could have the same size:
Another sample "p" response (from student 1133) showing how the brighter, larger star could have the same temperature:

Physics midterm problem: placing meters between batteries

Physics 205B Midterm 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 18.31, 18.72, 18.73

Two nickel-metal hydride (NiMH) batteries[*] each with an emf of 1.2 volts and an internal resistance of 0.1 Ω are connected to a 16.0 Ω light bulb[**], with an open gap between the batteries. In this gap, either an ideal voltmeter, or an ideal ammeter is to be connected. Determine (a) the voltmeter reading when it is connected between the batteries, and (b) the ammeter reading when it is connected between the batteries. Show your work and explain your reasoning using the properties of currents and potential differences, and Kirchhoff's rules and Ohm's law.

[*] "Cell charged: 100 milliohms," ti.com/lit/an/slva194/slva194.pdf.
[**] goo.gl/jLtakj.

Solution and grading rubric:

• p:
  Correct. Applies Kirchhoff's loop rule and the fact that no current would flow through circuit (a) due to the infinite resistance of the ideal voltmeter to determine that should read 2.4 V; applies equivalent resistance and Ohm's law to determine the current flowing through the ideal (zero resistance) ammeter in circuit (b) should be 0.15 A.
• r:
  Nearly correct, but includes minor math errors.
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Voltmeter reading in circuit (a) is zero ("no current flow" = no voltage differences), infinite ("no current flow" = infinite/undefined voltage differences), or some value slightly less than 2.4 V due to internal resistance voltage drops (which would only be true if current were flowing through them), but still has the correct ammeter reading for circuit (b).
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Some attempt at using Kirchhoff's rules, Ohm's law, and equivalent resistance.
• x:
  Implementation of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Sections 30882, 30883
Exam code: midterm02iF47
p: 3 students
r: 2 students
t: 23 students
v: 10 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 7979):

Presentation: Cuesta College modern physics laboratory equipment proposal

(Splash screen: cathode ray tube television and magnet.)

This is a grant proposal presented to the Cuesta College Foundation for purchasing equipment for a new laboratory component to the modern physics curriculum.

First, explaining the need for this new equipment.

Cuesta College has a two-semester calculus-based introductory physics lecture with a laboratory component for engineering and physics majors. The terminal third semester covers modern physics but is a lecture-only class, with no laboratory component.

Recently an Associate Degree for Transfer has been recently established between California Community Colleges and the California State University system, where students who complete their community college coursework can be guaranteed admission to a state university campus with junior status. In order for the physics curriculum at Cuesta College to be recognized as an Associate Degree for Transfer program, the third semester of modern physics must now include a laboratory component, which has historically never been offered before at Cuesta College.

Second--with the pressing need to start-up a laboratory course in modern physics at Cuesta College--what type of equipment would this require?

Modern physics is "modern" not just in the sense of 20th-century scientific discoveries, but also these discoveries were harbingers of the technology used everyday in our modern 21st world.

Nobel physics prizes were awarded in recognition of the significance of these discoveries, and a "modern" physics laboratory should allow students to experience what these physicists experienced in making their breakthroughs. Let's consider a sample of these Nobel physics prize winners, their experimental findings, and what it would take for students to recreate these discoveries in a modern physics laboratory setting.

Here's J. J. Thomson, the 1906 Nobel physics prize winner at his element in his laboratory, investigating the effect of magnetic fields on electron streams.

Measuring the behavior of this electron stream established that electrons were particles with a given ratio of mass per charge. In fact, this experimental set-up is the basis for cathode ray tube televisions, where a stream of electrons down a tube hits a screen, and using magnetic fields to sweep this beam across the screen can build up a moving image. So when students are recreating Thomson's experiment, they are also experiencing hands-on principles of early television technology. Certainly we can't have students building a television from scratch in order to measure electron mass/charge ratios, so it is necessary to purchase a ready-made set-up designed for students to tinker with and perform measurements safely.

Next, Robert A. Millikan, the 1923 Nobel physics prize winner, giving a lecture on his discoveries, including measuring the charge of electrons.

Millikan's apparatus allowed him to carefully measure the exact amount of charge on an electron, using a microscope to track the motion of tiny oil droplets that are attracted to electrically charged plates. Interestingly, this experimental set-up is the basis for photocopiers, where tiny toner particles are attracted to electrically charged plates that transferred onto paper sheets. So when students are recreating Millikan's experiment, they are also experiencing hands-on the principles of early photocopier technology. Again, it would be impractical for students to build a photocopier from scratch in order to measure the charge of electrons, so it is necessary to purchase a ready-made set-up designed for students to tinker with and perform measurements safely.

Here we have Max Planck (1918 Nobel physics prize winner) together with Albert Einstein (1921 Nobel physics prize winner). While they each have a long list of contributions to modern physics, together Planck and Einstein are associated with the fundamental quantum mechanical nature of light.

The apparatus required to do this entails shining low-intensity light of different wavelengths onto the electrons on clean metal surfaces. If the intensity of light is low enough, the light hits the metal surface as individual photons, and these photons can release electrons off of the surface if they have a sufficient amount of energy. Notably, the principles of this experimental set-up is used in many devices such as night vision goggles, where the interactions between individual photons and electrons are used to record images in extremely low-light conditions. So when students are recreating this experiment, they are also experiencing hands-on the principles of night-vision goggles and other similar imaging devices. Yet again, it would be impractical for students to build a night-vision viewer from scratch in order to discover the photon nature of light, so it is necessary to purchase a ready-made set-up designed for students to tinker with and perform measurements safely.

Third and last, how much will this cost, and how many experimental set-ups are needed?

The original grant proposal requests a sum of $30,000 in order to purchase modern physics laboratory equipment that would support the current Physics 208C curriculum. As we have seen, a lower-end cost for each experimental set-up is $800-$1,000. At the minimally reduced funding level, $10,000-$12,000 would purchase twelve key modern physics set-ups. Yet with an enrollment of 24-30 students, each week in laboratory there would be 8-10 groups of students sharing a single experimental set-up. This can be done if student groups use the equipment in rotation along with other tasks during instruction, but this means that each group would only have a few minutes to use the equipment, instead of being able to individually build up, tinker with, and fine-tune their experimental set-ups. Twice this minimal funding level would allow two experimental set-ups for the students to use each week (increasing throughput 200%!), and the full grant request of $30,000 would allow three experimental set-ups to be shared among the 8-10 groups. Thus we request the full $30,000 in order to maximize the educational benefit to these students, giving them as much exposure to these important modern physics discoveries.

Also safety...

...and durability of equipment would obviously be taken into consideration during purchasing, as these experiments are to be a substantive investment in the educational experience of Cuesta College students for many years to come.

Questions or comments?

Thank you for this opportunity to address the Foundation on funding the purchase of equipment for the new modern physics laboratory component to Physics 208C.

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06Lp4s



Sections 30882, 30883 results

0- 6 :	* [low = 6]
7-12 :	******
13-18 :	**************** [mean = 17.8 +/- 5.4]
19-24 :	***********
25-30 :	** [high = 30]