Light, the Universe, and Everything
I 142-Spring 2004
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HOMEWORK ASSIGNMENTS |
Hints, Comments, Notes |
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Photons from the edge of infinity The above link will take you to the final homework problem, which is due at the end of the exam period. You may return it as an e-mail attachment to tdennis, in which case you should name the attachment file YourlastnameFinal If you have paper to turn in, you may take it to my 221 Kendade office --- NOT the Observatory. |
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Emission Line Photons Suppose that a hydrogen atom in the Orion Nebula is (as most atoms are at any given moment) in the ground state (level 1 in fig. 7U.15.11). It absorbs from one of the stars of the nebula enough starlight energy to make a "quantum jump" to level 6. 1. How much energy must that photon have been transporting? Calculate the answer from equation 7U.15.3; embed your calculation in a grammatical and well structured English sentence. 2. Suppose that from level 6 the atom jumps successively down to level 5, level 3, level 2, and finally level 1. Calculate the energy involved in each of these jumps. This time show your results in the first three columns of a table of four columns (the last column will be used for part 5, below). Do the work on a separate piece of scratch paper, which you should keep but need not hand in. In the last row of the table, write the results of your calculation for part one. 3. Check your work by comparing your answers in 1. and 2. Do things check as they should? Write your answer as a single sentence, including the arithmetical calculations. 4. Using one of the entries from the table of part 2, calculate the wavelength of the photon which must be emitted. Again, embed your calculation in a grammatical and well structured English sentence. 5. Now fill in the fourth column of the table, following the ground rules of part 2. 6. It turns out that only one of the 6 photons in this problem is visible light. Which is it? What color does it appear to be? In what parts of the spectrum do the other photons lie? Express your answer as a single well-structured paragraph. Due Monday 4/19 by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnameEmission |
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Photons Write out one or two sentence answers to each of the questions in section 5 of the write-up for Lab 5 , "Photoelectric Effect". Due Monday 4/12 by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnamePhotons |
Re-read Chapters SR. 3 and 7U.14 and the first four pages of the write-up for Lab 5 before you begin to write. |
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Indoor lighting
How does indoor lighting compare to sunlight? This is the emission spectrum produced by an old-fashioned 60 Watt incandescent tungsten filament light bulb. The dashed vertical lines on the graph indicate the range of visible light. Either print out this figure or copy and paste it into a Word document. Label the violet and red ends of the spectrum, and indicate their wavelengths. Calculate the temperature (in Kelvins) of this bulb, using Wien's law. The sun has a temperature of approximately 5770K. According to Wien's law, at what wavelength should it produce the most light? Due Friday 4/9 by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnameBulb |
Read Chapters 12 & 14 in 7U's. Do your calculations, then write a little essay, incorporating your results into it, and referring to the graph as appropriate. Consider the relationship between heat and light. 1 mm = 1000 microns |
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Maxwell's Equations Rendered into English Write a brief essay showing how the terms in this set of equations can be related to the experiments we have done with rabbit fur, balloons, pipe stems, wool sweaters, coils of wire, compass needles, iron filings, cow magnets, etc. The most important goals are to explain the relationships clearly, and to be as specific as possible. Give it a try in preparation for Wednesday's class, so you can raise questions as necessary. Due Friday 4/2 by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnameE&M |
Use your notes, your electricity lab handout and the info in chapter 7U.11 (the equations on the ...and there was light! slide are the same as equations 7.11.1-4) The symbols you may want can be found in the symbol font in Word. Insert/symbol Font:symbol
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Rays or Waves? Briefly describe some (3 to 5) of the successes of ray theory, or phenomena that can be explained by it. What are some (2 or 3) phenomena for which wave theory works and ray theory doesn't? Explain. How can these two theories of light be reconciled? Due Monday 3/29 by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnameRayWave |
Reread the labs Making Waves and Newton's Opticks. Reread SR 2, and 7U.7, 9 & 10 |
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Are the stars distant suns?
Due Wednesday 3/10 by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnameDistantSuns |
Read 7U 8 & 9, paying special attention to Aristotle's mistake and Bruno's fate. The mathematical techniques are shown in 7U.9. Do all the calculations and tabulating first. (Take advantage of homework help if you need to!) Then craft an essay to address the question. Use the results of your calculations as specific evidence to back up your answer (which should be more nuanced than "yes" or "no"). |
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Aristotle's Mistake
Due Mon 3/8 by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnameAristotle |
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The organization of the retina. Write a short paper describing the distribution of the different receptors on the retina. Explain how the various phenomena of vision that we experienced in What's Where on your Retina demonstrate (or at least are consistent with) retinal anatomy. Write as if for another student who was not present during our demonstrations, explaining how she might see these things for herself. Due Mon 3/1 by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnameRetina |
Re-read the lab (What's Where ...) and ch 6 (Sex, Eyes, ...). You may find the illustrations here useful. Be sure you can answer the study questions at the end of the lab. Do not feel obligated to follow the order either in the study guide or the lab. See Holly for help getting your ideas and observations well-organized. |
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Newton's Color Theory In our lab called Newton's Opticks, there is a list of Newton's propositions regarding color, written in a style appropriate to the time and the prevailing views of his audience. Give a more modern account of Newton's theory, that is, restate his theory for an audience of your contemporaries, not his. Use examples (of phenomena that you have observed) that clearly illustrate his principles, and show how anyone might demonstrate them. Fri 2/27/04 by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnameNewton |
7U.7 and SR 1, 8, & 9 contain pertinent material. (Look for the Newton quotes in SR 8 & 9.) Don't feel obliged to have the same number of propositions as Newton, or to write them in the same order. Write as if for someone who is not in our class, but who is interested in theories of color. If you need to call upon modern color theory, be sure to show how it agrees with or differs from Newtonian color theory. |
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Jokes, Stories, or Songs Come prepared to entertain your classmates using just your voice. for Wed 2/25/04 |
In order to demonstrate our dim-light vision, we will have to sit in the dark for at least 7 minutes while our rods crank up to speed. To avoid boredom-induced damage to our sanity, we need 7 minutes of entertainment. |
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The apparent size of Mars. 1. As you can see from this scale drawing of the solar system, Mars' rather highly elongated orbit of the sun lies just beyond the earth's. On the basis of this drawing, make a sketch showing the positions of earth and Mars when Mars presents us earthlings with its largest apparent angular diameter; and on the same sketch draw in the corresponding observer's triangle. 2. On the screen of your monitor, or on a print-out, measure the closest possible distance between Mars and the earth and the radius of the earths's orbit; then use this information to calculate the shortest possible earth-mars distance in units of astronomical units (a.u.). 3. Convert this distance into units of meters, using the method of magic ones. 4. Use the Observer's Triangle formula to calculate the largest possible apparent angular diameter of Mars, in units of degrees. 5. Finally, write it up as a short essay including the diagram, an explanation of your procedure, and your calculations smoothly incorporated into the text of the essay. Due Friday 2/20, by 5 pm to the Observatory, or by midnight as an email attachment to tdennis. Name the file: YourlastnamePlanetAngles |
[Hint:] You'll have to think about where both the earth and Mars might be located. Your answer will be less than 1 a.u. See 7U. 5 to refresh yourself on the Observer's Triangle. See 7U. 6.4 for the definition of a.u., and all the data and conversion factors you may need. |
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Lying Down in Microspace Do problem 15 on page 250. As before, your answer should be in the form of a little essay, in which the math is embedded as necessary. Due Mon, 2/16 , by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnameScale |
Pay careful attention to units, and remember that the scale factor is unitless. Homework help is available Th & Sun evenings in the Observatory. |
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Protons across the universe Read Chapter 1 in 7U, paying particular attention to section 7U.1.4 (including the worked problems on page 232), then do problem 8 on page 249. Write up your answer as a little essay, using the math as appropriate. Friday 2/13, by 5 pm to the Observatory, or by midnight as an email attachment to kdorfman. Name the file: YourlastnamePopBeads |
Help with units can be found in chapter 7U.3. Help with exponents can be found in 7U.4. You can write equations in Word with Insert>Object>Microsoft_ Equation. Each cell in the Equation toolbar is a drop-down menu. |
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Pinhole Camera In lab, we used geometrical principles to predict that an object would make an image inside a pinhole camera. We also looked at an object (a black paper arrow taped to the window) through a real pinhole camera, and saw the image inside. The paper arrow was 240 mm tall; we stood about 2 meters from it; the distance from the pinhole to the ground glass screen was 160 mm. How tall was the image on that screen? Your eye is about 24 mm in diameter. When you look at the arrow from the same distance with just your eye, how big an image should it make on your retina? (Assume for this purpose that your eye is just like a pinhole camera.) Incorporate your answer into a little essay, which explains what you did and why. Embed the math in the paragraphs as needed. Due Monday 2/9 |
Begin by drawing a diagram, and labeling it with the appropriate distances. Then do the calculations. Now you are ready to write up your answer. See here for sample answers to Problem 9, p. 249. Help with units can be found in chapter 7U.3. This Math Style Sheet may also offer some advice (perhaps more than you need at this point). Call Holly Parkis for consultation. |
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How'd they do this? Due Fri 2/6, as an email attachment. to kdorfman. Name the attachment: YourlastnameColormix |
Use color mixing theory to explain how this
image is produced on the computer monitor, and how it would be
produced with ink on the printed page. Do so in a way that unifies
the two methods of color reproduction into a cohesive explanatory
framework. Color monitor handout Color printing handout |
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Do the exercises on this sheet, and bring it (or the answers on a separate piece of paper) to class. We will give the official writing assignment after we have reviewed this material in class. Due Monday 2/2, in class |
The projectors and filters will be available to you in class, so you can repeat any experiments or test any predictions you wish. |
