"G = 6.67(10^11)" by AnonymousSpring Semester 2008
Cuesta College, San Luis Obispo, CA
Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.
20080430
Erasing slate: universal gravitational constant
"G = 6.67(10^11)" by AnonymousSpring Semester 2008
Cuesta College, San Luis Obispo, CA
Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.
Astronomy midterm question: star cluster age
Astronomy 10 Midterm 3, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[15 points.] In cluster 1, the main sequence extends from spectral class O to spectral class K. In cluster 2, there are no main sequence stars cooler than spectral class F. Determine which star cluster is older, and explain the reasoning behind your choice.
Solution and grading rubric:
Section 4160
p: 5 students
r: 9 students
t: 10 students
v: 14 students
x: 1 student
y: 1 student
z: 0 students
A sample "p" response (from student 1223):
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[15 points.] In cluster 1, the main sequence extends from spectral class O to spectral class K. In cluster 2, there are no main sequence stars cooler than spectral class F. Determine which star cluster is older, and explain the reasoning behind your choice.
Solution and grading rubric:
- p = 15/15:
Correct. The OBAFGKM main sequence runs from massive to medium to low-mass. Massive stars become main sequence stars sooner, and spend less time as main sequence stars than medium mass stars. Since cluster 1 (OBAFGK) has more medium-mass stars on the main sequence than cluster 2 (OBAF), then cluster 1 must be older, as more time was required for its spectral class G and K stars to reach its main sequence. - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Recognizes the relationship between mass (inferred from spectral type -> temperature -> luminosity -> mass along the main sequence line), and main sequence lifetime, but rest of discussion is garbled or incomplete. - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least mentions some understanding of the relationships between mass and evolution times. - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 4160
p: 5 students
r: 9 students
t: 10 students
v: 14 students
x: 1 student
y: 1 student
z: 0 students
A sample "p" response (from student 1223):
Astronomy midterm question: cool star brighter than a hot star?
Astronomy 10 Midterm 3, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[15 points.] How is it possible that a cool star can be more luminous than a hot star? Using an H-R diagram, explain your reasoning with Wien's law and/or the Stefan-Boltzmann law
Solution and grading rubric:
Section 4160
p: 19 students
r: 10 students
t: 7 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 1231):
Another "p" response (from student 4607), using what appears to be a luminosity versus wavelength graph (due to the Planck curves) rather than a luminosity versus temperature (H-R digram) graph:
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[15 points.] How is it possible that a cool star can be more luminous than a hot star? Using an H-R diagram, explain your reasoning with Wien's law and/or the Stefan-Boltzmann law
Solution and grading rubric:
- p = 15/15:
Correct. The Stefan-Boltzmann law states that luminosity depends on both the size (surface area) of the star, and its temperature. Thus a merely warm star can still be more luminous than a hotter star if the warm star is much bigger in size than the hotter star. - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Stefan-Boltzmann law is garbled, but at least understands how size can be independent from temperature in determining the luminosity of a star. - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Discussion based somehow on Wien's law and/or the Stefan-Boltzmann law. - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Typically confuses luminosity with apparent magnitude by saying that the warm star could be closer to the Earth than the hotter star, when in fact luminosity (and absolute magnitude) are unaffected by distance. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 4160
p: 19 students
r: 10 students
t: 7 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 1231):
Another "p" response (from student 4607), using what appears to be a luminosity versus wavelength graph (due to the Planck curves) rather than a luminosity versus temperature (H-R digram) graph:
20080429
Astronomy midterm question: Sun as a pulsar?
Astronomy 10 Midterm 3, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.5
[15 points.] Decide whether our Sun will ever become a pulsar. If so, then discuss how this process will occur. If not, then discuss why this process cannot occur. Explain using the properties and evolution of stars.
Solution and grading rubric:
Section 4160
p: 9 students
r: 3 students
t: 10 students
v: 9 students
x: 7 students
y: 1 student
z: 1 student
Section 5166
p: 11 students
r: 5 students
t: 14 students
v: 22 students
x: 3 students
y: 0 students
z: 0 students
A sample "p" response (from student 0223):
Another "p" response (from student 4607), perhaps looking to be disappointed when the Sun does not go out with a bang:
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.5
[15 points.] Decide whether our Sun will ever become a pulsar. If so, then discuss how this process will occur. If not, then discuss why this process cannot occur. Explain using the properties and evolution of stars.
Solution and grading rubric:
- p = 15/15:
Correct. Adequately describes either what the Sun would eventually become (white dwarf), or why the Sun cannot become a neutron star (pulsar). - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least demonstrates understanding that the Sun is not massive enough to become a supergiant -> type II supernova -> neutron star, and/or understands the properties of a pulsar that presumably cannot be attained by the medium-mass Sun. - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Explains that the Sun will become a pulsar, or explains that the Sun cannot become a pulsar because it is too massive. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 4160
p: 9 students
r: 3 students
t: 10 students
v: 9 students
x: 7 students
y: 1 student
z: 1 student
Section 5166
p: 11 students
r: 5 students
t: 14 students
v: 22 students
x: 3 students
y: 0 students
z: 0 students
A sample "p" response (from student 0223):
Another "p" response (from student 4607), perhaps looking to be disappointed when the Sun does not go out with a bang:
20080428
Astronomy midterm question: H-R turnoff points
Astronomy 10 Midterm 3, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[15 points.] Show what the turnoff point of a star cluster is on an H-R diagram, and explain how this can be used to estimate the age of the stars in the cluster.
Solution and grading rubric:
Section 5166
p: 9 students
r: 4 students
t: 15 students
v: 10 students
x: 7 students
y: 7 students
z: 3 students
A sample "p" response (from student 9518):
A sample "y" response (froms student ), who like many others felt compelled to write something down (for minimal partial credit) rather than leave the answer blank:
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[15 points.] Show what the turnoff point of a star cluster is on an H-R diagram, and explain how this can be used to estimate the age of the stars in the cluster.
Solution and grading rubric:
- p = 15/15:
Correct. "Turnoff point" is where stars from a cluster deviate from the main-sequence line. A turnoff point near the top left indicates a young cluster, as the massive stars have not yet reached their supergiant phases, turnoff point near the bottom right indicates an older cluster, as only the low-mass stars are still on the main sequence. Clearly indicates/draw/describes what a typical turnoff point looks like, and how its position is correlated with age. May instead describe how the different evolution tracks/rates of different mass stars that are observed on the main sequence line can be used to determine the age of a star cluster, without explicit mention of the "turnoff point." - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least understands mass determines evolution tracks/rates. - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 5166
p: 9 students
r: 4 students
t: 15 students
v: 10 students
x: 7 students
y: 7 students
z: 3 students
A sample "p" response (from student 9518):
A sample "y" response (froms student ), who like many others felt compelled to write something down (for minimal partial credit) rather than leave the answer blank:
20080427
Astronomy midterm question: cooler, brighter star versus dimmer, hotter star
Astronomy 10 Midterm 3, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[15 points.] How is it possible that a more luminous star can be cooler than a less luminous star? Using an H-R diagram, explain your reasoning with Wien's law and/or the Stefan-Boltzmann law.
Solution and grading rubric:
Section 5166
p: 21 students
r: 10 students
t: 9 students
v: 11 students
x: 2 students
y: 1 student
z: 1 student
A sample "p" response (from student 1315):
This same student, like many others, made a thumbnail note of Wien's law and the Stefan-Boltzmann law on their exam paper at the start of the midterm. Note the explicit use of the word "proportional" instead of the symbol, which some students this semester called "The Pliers."
Another student 1652, after writing a "p" response, decried the abstractness and irrelevance of astronomy at this point in the semester.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[15 points.] How is it possible that a more luminous star can be cooler than a less luminous star? Using an H-R diagram, explain your reasoning with Wien's law and/or the Stefan-Boltzmann law.
Solution and grading rubric:
- p = 15/15:
Correct. The Stefan-Boltzmann law states that luminosity depends on both the size (surface area) of the star, and its temperature. Thus a cooler star can still be more luminous than a hotter star if the cooler star is much bigger in size than the hotter star. - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Stefan-Boltzmann law is garbled, but at least understands how size can be independent from temperature in determining the luminosity of a star. May confound mass with size in discussion. - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Discussion based somehow on Wien's law and/or the Stefan-Boltzmann law. - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Typically confuses luminosity with apparent magnitude by saying that the cooler star could be closer to the Earth than the hotter star, when in fact luminosity (and absolute magnitude) are unaffected by distance. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 5166
p: 21 students
r: 10 students
t: 9 students
v: 11 students
x: 2 students
y: 1 student
z: 1 student
A sample "p" response (from student 1315):
This same student, like many others, made a thumbnail note of Wien's law and the Stefan-Boltzmann law on their exam paper at the start of the midterm. Note the explicit use of the word "proportional" instead of the symbol, which some students this semester called "The Pliers."
Another student 1652, after writing a "p" response, decried the abstractness and irrelevance of astronomy at this point in the semester.
20080425
Astronomy clicker question: type II supernova energy source
Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] A supergiant will eventually explode as a type II supernova. What provides the energy for this explosion?
(A) Radioactive decays of unstable heavy elements.
(B) Fusion of light elements into heavy elements.
(C) Sudden gravitational contraction.
(D) Dark energy.
Correct answer: (C)
Student responses
Section 4160
(A) : 5 students
(B) : 9 students
(C) : 13 students
(D) : 3 students
Section 5166
(A) : 7 students
(B) : 16 students
(C) : 25 students
(D) : 6 students
Response (D) is merely a ruse (as it had not yet been covered yet in this course sequence). Response (A) is fission, which is not a source of energy for a star. Response (D) is fusion, which can no longer provide energy for a star at the end of its supergiant phase, as it core is iron at this point, past which requires more energy to be put in than can be released by fusion. Thus with no energy source to balance gravity, the core undergoes runaway contraction (becoming a neutron star in the process), and the resulting energy from this gravitational collapse of the core is transferred to the outer layers of the supergiant in an "implosion-explosion" sequence--a type II supernova.
Previous post: Type II supernova simulators.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] A supergiant will eventually explode as a type II supernova. What provides the energy for this explosion?
(A) Radioactive decays of unstable heavy elements.
(B) Fusion of light elements into heavy elements.
(C) Sudden gravitational contraction.
(D) Dark energy.
Correct answer: (C)
Student responses
Section 4160
(A) : 5 students
(B) : 9 students
(C) : 13 students
(D) : 3 students
Section 5166
(A) : 7 students
(B) : 16 students
(C) : 25 students
(D) : 6 students
Response (D) is merely a ruse (as it had not yet been covered yet in this course sequence). Response (A) is fission, which is not a source of energy for a star. Response (D) is fusion, which can no longer provide energy for a star at the end of its supergiant phase, as it core is iron at this point, past which requires more energy to be put in than can be released by fusion. Thus with no energy source to balance gravity, the core undergoes runaway contraction (becoming a neutron star in the process), and the resulting energy from this gravitational collapse of the core is transferred to the outer layers of the supergiant in an "implosion-explosion" sequence--a type II supernova.
Previous post: Type II supernova simulators.
Erasing slate: Elmo, presumably
"Untitled" by AnonymousSpring Semester 2008
Cuesta College, San Luis Obispo, CA
Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.
20080423
Erasing slate: smiley eyebrow girl
"Untitled" by AnonymousSpring Semester 2008
Cuesta College, San Luis Obispo, CA
Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.
20080421
Astronomy quiz question: stellar evolution times
Astronomy 10 Quiz 9, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[Version 1]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the least amount of time?
(A) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a low mass protostar as it becomes a main sequence star.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the least amount of time.)
Correct answer: (A)
Due to their greater gravitational forces, massive protostars take a relatively short amount of time to contract and heat up to initiate fusion; and also their rapid fusion rates will cause them to have a relatively short main sequence lifetime (cf. previous post on main sequence lifetimes). In contrast, medium-mass stars will take longer than that just to get from the protostar to the main sequence stages, while low-mass stars take a even longer amount of time.
Student responses
Section 4160
(A) : 25 students
(B) : 3 students
(C) : 7 students
(D) : 0 students
(E) : 0 students
[Version 2]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the most amount of time?
(A) The track taken by a low mass protostar as it becomes a main sequence star.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the most amount of time.)
Correct answer: (A)
Section 5166
(A) : 34 students
(B) : 2 students
(C) : 11 students
(D) : 5 students
(E) : 3 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[Version 1]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the least amount of time? (A) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a low mass protostar as it becomes a main sequence star.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the least amount of time.)
Correct answer: (A)
Due to their greater gravitational forces, massive protostars take a relatively short amount of time to contract and heat up to initiate fusion; and also their rapid fusion rates will cause them to have a relatively short main sequence lifetime (cf. previous post on main sequence lifetimes). In contrast, medium-mass stars will take longer than that just to get from the protostar to the main sequence stages, while low-mass stars take a even longer amount of time.
Student responses
Section 4160
(A) : 25 students
(B) : 3 students
(C) : 7 students
(D) : 0 students
(E) : 0 students
[Version 2]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the most amount of time? (A) The track taken by a low mass protostar as it becomes a main sequence star.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the most amount of time.)
Correct answer: (A)
Section 5166
(A) : 34 students
(B) : 2 students
(C) : 11 students
(D) : 5 students
(E) : 3 students
20080420
Astronomy quiz question: heavy nuclei fusion
Astronomy 10 Quiz 9, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.4
[3.0 points.] Which one of the following choices best explains why nuclei of elements heavier than hydrogen require higher temperatures to undergo fusion?
(A) Stronger repulsive forces between nuclei.
(B) Stronger gravitational forces between nuclei.
(C) Less energy is contained in heavier nuclei.
(D) More energy is contained in heavier nuclei.
(E) Stronger degeneracy pressures between nuclei.
Correct answer: (A)
All atomic nuclei repel each other, due to their positively charged protons. The relative amount of repulsion between two same-element nuclei depends on the square of the protons contained in a nucleus; it is this repulsion that must be overcome in order for fusion to be initiated.
Student responses
Section 4160
(A) : 17 students
(B) : 5 students
(C) : 2 students
(D) : 4 students
(E) : 8 students
Section 5166
(A) : 30 students
(B) : 5 students
(C) : 2 students
(D) : 16 students
(E) : 4 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.4
[3.0 points.] Which one of the following choices best explains why nuclei of elements heavier than hydrogen require higher temperatures to undergo fusion?
(A) Stronger repulsive forces between nuclei.
(B) Stronger gravitational forces between nuclei.
(C) Less energy is contained in heavier nuclei.
(D) More energy is contained in heavier nuclei.
(E) Stronger degeneracy pressures between nuclei.
Correct answer: (A)
All atomic nuclei repel each other, due to their positively charged protons. The relative amount of repulsion between two same-element nuclei depends on the square of the protons contained in a nucleus; it is this repulsion that must be overcome in order for fusion to be initiated.
Student responses
Section 4160
(A) : 17 students
(B) : 5 students
(C) : 2 students
(D) : 4 students
(E) : 8 students
Section 5166
(A) : 30 students
(B) : 5 students
(C) : 2 students
(D) : 16 students
(E) : 4 students
20080419
Astronomy quiz question: rapid fusion rates
Astronomy 10 Quiz 9, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.3
[3.0 points.] Which one of the following choices best explains why the fusion rate in the core of a massive main sequence star is more rapid than the core of a less massive main sequence star?
(A) The core of a massive main sequence star contains more hydrogen.
(B) The core of a massive main sequence star is younger.
(C) The core of a massive main sequence star has a higher temperature and pressure.
(D) The core of a massive main sequence star does not have as much convection currents to stir up hydrogen.
(E) The core of a massive main sequence star does not have as much degeneracy pressure.
Correct answer: (C)
(Cf. previous post on main sequence lifetimes.)
Student responses
Section 5166
(A) : 12 students
(B) : 1 student
(C) : 39 students
(D) : 2 students
(E) : 1 student
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.3
[3.0 points.] Which one of the following choices best explains why the fusion rate in the core of a massive main sequence star is more rapid than the core of a less massive main sequence star?
(A) The core of a massive main sequence star contains more hydrogen.
(B) The core of a massive main sequence star is younger.
(C) The core of a massive main sequence star has a higher temperature and pressure.
(D) The core of a massive main sequence star does not have as much convection currents to stir up hydrogen.
(E) The core of a massive main sequence star does not have as much degeneracy pressure.
Correct answer: (C)
(Cf. previous post on main sequence lifetimes.)
Student responses
Section 5166
(A) : 12 students
(B) : 1 student
(C) : 39 students
(D) : 2 students
(E) : 1 student
20080418
Astronomy quiz question: massive and luminous stars
Astronomy 10 Quiz 9, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.3
[3.0 points.] Which one of the following statements best explains why the most massive main sequence stars are also the most luminous main sequence stars?
(A) They fuse hydrogen more rapidly.
(B) They are the youngest stars.
(C) They contain more unstable radioactive isotopes.
(D) They release more energy from gravitational contraction.
(E) (None of the above choices (A)-(D), as the most massive main sequence stars are not the most luminous main sequence stars.)
Correct answer: (A)
(Cf. previous post on main sequence lifetimes.)
Student responses
Section 4160
(A) : 25 students
(B) : 3 students
(C) : 2 students
(D) : 5 students
(E) : 1 student
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.3
[3.0 points.] Which one of the following statements best explains why the most massive main sequence stars are also the most luminous main sequence stars?
(A) They fuse hydrogen more rapidly.
(B) They are the youngest stars.
(C) They contain more unstable radioactive isotopes.
(D) They release more energy from gravitational contraction.
(E) (None of the above choices (A)-(D), as the most massive main sequence stars are not the most luminous main sequence stars.)
Correct answer: (A)
(Cf. previous post on main sequence lifetimes.)
Student responses
Section 4160
(A) : 25 students
(B) : 3 students
(C) : 2 students
(D) : 5 students
(E) : 1 student
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.
20080416
Vacuum in an air-filled room
Dinosaur Comics, by Ryan Northwww.qwantz.com
April 16, 2008 (excerpt)
Physics 8A learning goal Q12.1
Ryan North comments on popular unlikely disasters, among them the statistical improbability of experiencing a vacuum in a corner of an air-filled room, and swallowing a black hole.
Previous post: comment on Ryan North's Dinosaur Comics discussion of the the dark energy-accelerated heat death of the universe.
20080415
Astronomy in-class activity: energy flow within stars
Astronomy 10 In-class activity 20 v.07.04.03, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.2
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet describing the energy flow within a main sequence star such as our Sun. Students are instructed to look for connections and similarities, then to concentrate on specific differences.
The answers for the second page are shown below.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.2
Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet describing the energy flow within a main sequence star such as our Sun. Students are instructed to look for connections and similarities, then to concentrate on specific differences.
The answers for the second page are shown below.
20080414
Astronomy in-class activity: OBAFGKM poetry slam
Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
One Bottle of Absolut Frequently Gives Killer Mornings
--A. B.
Only Boys Act Foolish Girls Keep Mellow
--T. D.
Only Bubba's Admiration Fueled Gump's Killer Modern Recipe: New Shrimp Chocolate
--R. E.
Oh Bright Awareness Forgive Good Kind Minds
--R. F.
Originally: Beatles Are Four Guys Keeping Music Love-Themed
--C. G.
Once Boys Are Fat Girls Kiss More
--K. G.
Occasionally Bob Argues For Guavas, Kiwis & Mangos, Regularly Never Succeeds Consistently
--S. L.
Our Best Autism Friends Got Knowledgeable Minds
--A. L. M.
Obama Beat A Fat Girl Known As M[rs.] Clinton
--A. M.
Offer Brotherly Advice For Good Karma, Man
--C. M.
Only Big Angry Feminists Go Kicking Men
--V. P.
0s (Zeros) Belong Away From Grades...Kindly Make Less Tests
--E. R.
Out Back A Farmer Grows Killer Mushrooms
--C. S.
Only Bandits And Filchers Gather Kindling & Matches Right Near Stephen Colbert's Lime Trees
--A. B.
Only Blue Army Fans Get Killaminjaros Mate
--C. B.
Outerspace Beings Are Freaking Going to Kill Me
--R. E.
Out Back Against Farthest Galaxies Killer Monkey Reign Negligently Supreme
--D. R.
Octopus Babies Are Full-Grown Killing Machines
--J. R.
Previous post: Astronomy in-class activity: OBAFGKM poetry slam instructions.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
One Bottle of Absolut Frequently Gives Killer Mornings
--A. B.
Only Boys Act Foolish Girls Keep Mellow
--T. D.
Only Bubba's Admiration Fueled Gump's Killer Modern Recipe: New Shrimp Chocolate
--R. E.
Oh Bright Awareness Forgive Good Kind Minds
--R. F.
Originally: Beatles Are Four Guys Keeping Music Love-Themed
--C. G.
Once Boys Are Fat Girls Kiss More
--K. G.
Occasionally Bob Argues For Guavas, Kiwis & Mangos, Regularly Never Succeeds Consistently
--S. L.
Our Best Autism Friends Got Knowledgeable Minds
--A. L. M.
Obama Beat A Fat Girl Known As M[rs.] Clinton
--A. M.
Offer Brotherly Advice For Good Karma, Man
--C. M.
Only Big Angry Feminists Go Kicking Men
--V. P.
0s (Zeros) Belong Away From Grades...Kindly Make Less Tests
--E. R.
Out Back A Farmer Grows Killer Mushrooms
--C. S.
Only Bandits And Filchers Gather Kindling & Matches Right Near Stephen Colbert's Lime Trees--A. B.
Only Blue Army Fans Get Killaminjaros Mate--C. B.
Outerspace Beings Are Freaking Going to Kill Me--R. E.
Out Back Against Farthest Galaxies Killer Monkey Reign Negligently Supreme--D. R.
Octopus Babies Are Full-Grown Killing Machines--J. R.
Previous post: Astronomy in-class activity: OBAFGKM poetry slam instructions.
20080413
Astronomy in-class activity: OBAFGKM poetry slam instructions
Astronomy 10 In-class activity 19 v.07.04.05, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students are instructed for homework to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Previous post: OBAFGKM poetry slam (Fall Semester 2007).
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students are instructed for homework to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Previous post: OBAFGKM poetry slam (Fall Semester 2007).
20080412
Bon mots: space, time, and spacetime
"Space by itself and time by itself must sink into the shadows, while only a union of the two preserves independence."
--Hermann Minkowski
"There was a blithe certainty that came from first comprehending the full Einstein field equations, arabesques of Greek letters clinging tenuously to the page, a gossamer web. They seemed insubstantial when you first saw them, a string of squiggles. Yet to follow the delicate tensors as they contracted, as the superscripts paired with subscripts, collapsing mathematically into concrete classical entities--potential; mass; forces vectoring in a curved geometry--that was a sublime experience. The iron fist of the real, inside the velvet glove of airy mathematics."
--Gregory Benford, Timescape (1992)
"Haunted by ill angels only,
Where an Eidolon, named NIGHT,
On a black throne reigns upright,
I have reached these lands but newly
From an ultimate dim Thule-
From a wild clime that lieth, sublime,
Out of SPACE- out of Time..."
--Edgar Allen Poe, "Dreamland"
"I heard that in relativity theory space and time are the same thing. Einstein discovered this when he kept showing up three miles late for his meetings."
--Steven Wright
"You can measure distance by time. 'How far away is it?' 'Oh about 20 minutes."'But it doesn't work the other way. 'When do you get off work?' 'Around 3 miles.'"
--Jerry Seinfeld
"My grandmother started walking five miles a day when she was sixty. She's ninety-seven now, and we don't know where the hell she is."
--Ellen DeGeneris
--Hermann Minkowski
"There was a blithe certainty that came from first comprehending the full Einstein field equations, arabesques of Greek letters clinging tenuously to the page, a gossamer web. They seemed insubstantial when you first saw them, a string of squiggles. Yet to follow the delicate tensors as they contracted, as the superscripts paired with subscripts, collapsing mathematically into concrete classical entities--potential; mass; forces vectoring in a curved geometry--that was a sublime experience. The iron fist of the real, inside the velvet glove of airy mathematics."
--Gregory Benford, Timescape (1992)
"Haunted by ill angels only,
Where an Eidolon, named NIGHT,
On a black throne reigns upright,
I have reached these lands but newly
From an ultimate dim Thule-
From a wild clime that lieth, sublime,
Out of SPACE- out of Time..."
--Edgar Allen Poe, "Dreamland"
"I heard that in relativity theory space and time are the same thing. Einstein discovered this when he kept showing up three miles late for his meetings."
--Steven Wright
"You can measure distance by time. 'How far away is it?' 'Oh about 20 minutes."'But it doesn't work the other way. 'When do you get off work?' 'Around 3 miles.'"
--Jerry Seinfeld
"My grandmother started walking five miles a day when she was sixty. She's ninety-seven now, and we don't know where the hell she is."
--Ellen DeGeneris
20080411
Astronomy clicker question: main sequence lifetimes
Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M1.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the end of their learning cycle:
[0.3 points.] The main sequence lifetime of a star is how long it will be able to release energy from hydrogen fusion in its core. Which type of main sequence star will have the longest lifetime?
(A) A massive main sequence star.
(B) A medium-mass main sequence star.
(C) A low-mass main sequence star.
(D) The lifetime of a main sequence star does not depend on its mass.
Correct answer: (C)
Student responses
Section 4160
(A) : 11 students
(B) : 2 students
(C) : 17 students
(D) : 1 student
Section 5166
(A) : 19 students
(B) : 4 students
(C) : 18 students
(D) : 1 student
Explanations for typical student responses are elicited in a whole-class discussion after results have been posted.
Some students offer that they chose response (A) because the massive stars have more hydrogen to fuse, and thus will last the longest. Other students remark that they chose response (B) because low-mass stars have much slower fusion rates, and thus will be the most frugal and have the longest main sequence lifetime. (If both effects are important, perhaps the medium-mass star would live the longest?)
"Wasteful!" or "Live Fast, Die Young"
Due to their rapid fusion rates, massive stars have the shortest main sequence lifetimes, after the hydrogen in their cores has been depleted in hundreds of thousands to a few million years. They are the "wasteful" stars in the sense that there is still plenty of hydrogen in their outer layers, but this is unavailable to the core of the massive star to maintain its main sequence lifetime.
"Churn and Burn" or "Be Mellow, Live Forever"
However, low mass stars ("red dwarfs") have such slow fusion rates that they are cool and opaque enough for convection to stir up the entire star, such that fresh hydrogen is continuously cycled between the core and the rest of the star. Due to these two effects (slow fusion and a disproportionally larger amount of available hydrogen to fuse), low mass stars have extremely long main sequence lifetimes, measured in tens of billions of years. As the currently accepted age of the universe is 13-14 billion years, no low-mass stars are expected to have ever reached the end of their main sequence lifetimes yet!
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M1.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the end of their learning cycle:
[0.3 points.] The main sequence lifetime of a star is how long it will be able to release energy from hydrogen fusion in its core. Which type of main sequence star will have the longest lifetime?
(A) A massive main sequence star.
(B) A medium-mass main sequence star.
(C) A low-mass main sequence star.
(D) The lifetime of a main sequence star does not depend on its mass.
Correct answer: (C)
Student responses
Section 4160
(A) : 11 students
(B) : 2 students
(C) : 17 students
(D) : 1 student
Section 5166
(A) : 19 students
(B) : 4 students
(C) : 18 students
(D) : 1 student
Explanations for typical student responses are elicited in a whole-class discussion after results have been posted.
Some students offer that they chose response (A) because the massive stars have more hydrogen to fuse, and thus will last the longest. Other students remark that they chose response (B) because low-mass stars have much slower fusion rates, and thus will be the most frugal and have the longest main sequence lifetime. (If both effects are important, perhaps the medium-mass star would live the longest?)
"Wasteful!" or "Live Fast, Die Young"
Due to their rapid fusion rates, massive stars have the shortest main sequence lifetimes, after the hydrogen in their cores has been depleted in hundreds of thousands to a few million years. They are the "wasteful" stars in the sense that there is still plenty of hydrogen in their outer layers, but this is unavailable to the core of the massive star to maintain its main sequence lifetime.
"Churn and Burn" or "Be Mellow, Live Forever"However, low mass stars ("red dwarfs") have such slow fusion rates that they are cool and opaque enough for convection to stir up the entire star, such that fresh hydrogen is continuously cycled between the core and the rest of the star. Due to these two effects (slow fusion and a disproportionally larger amount of available hydrogen to fuse), low mass stars have extremely long main sequence lifetimes, measured in tens of billions of years. As the currently accepted age of the universe is 13-14 billion years, no low-mass stars are expected to have ever reached the end of their main sequence lifetimes yet!
20080409
Astronomy quiz question: photon emission/absorption
Astronomy 10 Quiz 8, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.4
[Version 1]
Which one of the following choices best describes what will happen to an electron in an atom that emits a photon?
(A) Transform into a proton.
(B) Emit blackbody radiation.
(C) Undergo a redshift or a blueshift.
(D) Move from an inner to an outer orbital.
(E) Move from an outer to an inner orbital.
Correct answer: (E).
Student responses
Section 4160
(A) : 0 students
(B) : 3 students
(C) : 1 student
(D) : 5 students
(E) : 6 students
Section 5166
(A) : 0 students
(B) : 4 students
(C) : 3 students
(D) : 7 students
(E) : 9 students
[Version 2]
Which one of the following choices best describes what will happen to an electron in an atom that absorbs a photon?
(A) Transform into a proton.
(B) Emit blackbody radiation.
(C) Undergo a redshift or a blueshift.
(D) Move from an inner to an outer orbital.
(E) Move from an outer to an inner orbital.
Correct answer: (D).
Student responses
Section 4160
(A) : 0 students
(B) : 1 student
(C) : 2 student
(D) : 14 students
(E) : 1 students
Section 5166
(A) : 4 students
(B) : 3 students
(C) : 3 students
(D) : 14 students
(E) : 3 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.4
[Version 1]
Which one of the following choices best describes what will happen to an electron in an atom that emits a photon?
(A) Transform into a proton.
(B) Emit blackbody radiation.
(C) Undergo a redshift or a blueshift.
(D) Move from an inner to an outer orbital.
(E) Move from an outer to an inner orbital.
Correct answer: (E).
Student responses
Section 4160
(A) : 0 students
(B) : 3 students
(C) : 1 student
(D) : 5 students
(E) : 6 students
Section 5166
(A) : 0 students
(B) : 4 students
(C) : 3 students
(D) : 7 students
(E) : 9 students
[Version 2]
Which one of the following choices best describes what will happen to an electron in an atom that absorbs a photon?
(A) Transform into a proton.
(B) Emit blackbody radiation.
(C) Undergo a redshift or a blueshift.
(D) Move from an inner to an outer orbital.
(E) Move from an outer to an inner orbital.
Correct answer: (D).
Student responses
Section 4160
(A) : 0 students
(B) : 1 student
(C) : 2 student
(D) : 14 students
(E) : 1 students
Section 5166
(A) : 4 students
(B) : 3 students
(C) : 3 students
(D) : 14 students
(E) : 3 students
20080408
Astronomy quiz question: stellar distances
Astronomy 10 Quiz 8, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.4
[Version 1]
Which one of the following choices best corresponds to an absolute magnitude +3 star that is the farthest away from the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.
Correct answer: (E).
Out of the above (A)-(E) choices, the star with a +6 apparent magnitude appears to be the dimmest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be farthest away if it appeared to be as dim as possible.
Student responses
Section 4160
(A) : 4 students
(B) : 3 students
(C) : 0 students
(D) : 1 students
(E) : 8 students
Section 5166
(A) : 4 students
(B) : 2 students
(C) : 1 student
(D) : 3 students
(E) : 13 students
[Version 2]
Which one of the following choices best corresponds to an absolute magnitude +3 star that is the closest to the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.
Correct answer: (A).
Out of the above (A)-(E) choices, the star with a -6 apparent magnitude appears to be the brightest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be nearest if it appeared to be as bright as possible.
Student responses
Section 4160
(A) : 6 students
(B) : 5 students
(C) : 3 students
(D) : 2 students
(E) : 3 students
Section 5166
(A) : 16 students
(B) : 2 students
(C) : 3 students
(D) : 3 students
(E) : 3 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.4
[Version 1]
Which one of the following choices best corresponds to an absolute magnitude +3 star that is the farthest away from the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.
Correct answer: (E).
Out of the above (A)-(E) choices, the star with a +6 apparent magnitude appears to be the dimmest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be farthest away if it appeared to be as dim as possible.
Student responses
Section 4160
(A) : 4 students
(B) : 3 students
(C) : 0 students
(D) : 1 students
(E) : 8 students
Section 5166
(A) : 4 students
(B) : 2 students
(C) : 1 student
(D) : 3 students
(E) : 13 students
[Version 2]
Which one of the following choices best corresponds to an absolute magnitude +3 star that is the closest to the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.
Correct answer: (A).
Out of the above (A)-(E) choices, the star with a -6 apparent magnitude appears to be the brightest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be nearest if it appeared to be as bright as possible.
Student responses
Section 4160
(A) : 6 students
(B) : 5 students
(C) : 3 students
(D) : 2 students
(E) : 3 students
Section 5166
(A) : 16 students
(B) : 2 students
(C) : 3 students
(D) : 3 students
(E) : 3 students
20080404
Mastering the Sky, Time, and Space with Starry Night(TM)
Presentation at the Central Coast Astronomical Society monthly meeting, March 27, 2008, 7:30-8:15 PM, Science Forum 2402, Cuesta College, San Luis Obispo, CA.
Starry Night(TM) from Imaginova Software (currently version 6.0) is a program that is bundled with many textbooks (usually as a previous version).
On the surface, Starry Night(TM) is a basic planetarium program that simulates viewing of the night sky, but is capable of much more than that--you can also bend time and space with it!
This is a simulated view of tonight's sky from San Luis Obispo, CA, using one of the pre-packaged local horizon panoramas, which can be viewed in any direction, and zoomed in or out. Starry Night(TM) can export a star chart, or even an interactive Quicktime VR file that preserves the three-dimensional aspect of viewing the celestial sphere from within.
You can also toggle star and constellation labels...
...as well as azimuth/altitude...
... and right ascension/declination grids.
Time can be run forwards or backwards at various rates, and a specific date and time can be selected.
Polaris is the current pole star, but what was the (nearest) pole star in 10,000 B.C.?
Alas, no true pole star in 10,000 B.C., but Vega is the closest brightest match.
After mastering the manipulation of the sky and time as with most other planetarium software, Starry Night(TM) also allows you to change your viewing position. This is made possible by generating an entire "sandbox" universe for you to move around in, and you can select (in the preferences) to render the trip from you old to your new location, which is often done at superluminal speeds.
Selecting Buenos Aires, Argentina will allow you to see southern hemisphere stars and constellations. 
After flying there over the surface of the Earth at supersonic speeds, we find that in the Buenos Aires sky there is no obvious "South Star" analog to Polaris.
Next we can travel to Mare Serenatatis (Sea of Serenity) on the Moon. In this case since the Moon is above the local horizon, we do not have to travel through the interior of the Earth to get there. 
Since we are on the near side of the Moon, due to its synchronous rotation, we can observe the Earth, which undergoes phases as it remains nearly stationary in its position high up in the sky, while the stars rise and set over a sidereal month.
Next let's travel to Nereid, an outer satellite of Neptune.
Nereid's rotation is not synchronous with Neptune, but is apparently in resonance. We can observe the stars rising in the east and setting in the west, as Neptune (orbited by Triton) rises in the west, stalls near the meridian, and the eventually sets in the west!
You are not just limited to traveling around the Solar System. The up/down "rocketship" controls allow you to fly up and away, to outside the Solar System...
...to outside the Milky Way...
...to beyond the mapped cubic volume of galaxy superclusters. It's like having your own Powers of Ten machine!
20080403
(Meteoroid), meteor, meteorite
The SimpsonsEpisode 4 (382), Season 18
"Treehouse of Horror XVII: Married to the Blob"
The Simpsons family witnesses a meteor landing in their backyard. Homer subsequently eats an alien lifeform found inside the meteorite, to tragicomedic results.
Previous post:
http://waiferx.blogspot.com/2008/03/astronomy-in-class-activity-meteorite.html
20080402
Aftermarket after-accident airbag deployment
The SimpsonsEpisode 13 (413), Season 19
"The Debarted"
Screencaps from hulu.com
Well after Hans Moleman's car is hit from behind by Marge Simpson, its airbag deploys to comedic results. (As Hans' car appears to be an AMC Gremlin, would that airbag an aftermarket add-on?)
Related posts:
Physics clicker question: airbag effect
Airbags make babies cry
20080401
Converging lens focal point
The SimpsonsEpisode 14 (414), Season 19
"Dial 'N' For Nerder"
Screencaps from hulu.com
Nelson Muntz encounters the "ant-burning spot," where nominally parallel rays from the Sun (behind Nelson? shadows?) converge to the far focal point, on a hapless ant (that manages to survive).
Subscribe to:
Posts (Atom)