Double-slit Interference. Class 26: (ThT Q) Are both coherence and monochromaticity essential?

Transcription

1 Double-slit Interference Class 26: (ThT Q) Are both coherence and monochromaticity essential?

2 Exam 2 Discussion #9. Consider an arbitrary engine whose work output is connected to a Carnot engine running in reverse. D, both a & b break 2 nd Law of thermodynamics. 21% rated poor discrimination.

3 Addition on Page 24 of Chapter Summaries If we turned around and began slowly to compress, the gas would just slowly exhaust heat to the environment in the exact reverse way that it absorbed it during expansion. In the Carnot cycle the amount of entropy removed from the hot reservoir is the same deposited into the cold reservoir. In all other cycles more entropy is deposited than extracted: Q h /T h Q c /T c, with the equal sign only true for the Carnot cycle. Most processes are irreversible. For example, if a gas-filled box were suddenly increased..

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5 Assume a sample of an ideal gas is at room temperature. What action will necessarily make the entropy of the sample increase? (a) transfer energy into it by heat (b) transfer energy into it irreversibly by heat (c) do work on it (d) decrease either its temperature or its volume, without letting the other variable decrease (e) none of these choices. B 47% very difficult.

6 #37& 38: A heat pump has a coefficient of performance equal to The refrigerator takes in 120 J of energy from a cold reservoir in each cycle. Find the work required in each cycle (LMD) 30 88% & The energy expelled to the hot reservoir. SLMD Q h = W+Q c = J=150J 44%; 0 29%; 2 12%; 9 7%

7 Did you complete at least 70% of Chapter 37:1-3? A.Yes B.No Lab 5: Diffusion of waves 2-slit diffraction multislit diffraction.

8 Lab 5 ends Friday night. 6 begins. Saturday Today: Physical optics: Diffraction 1.

9 Physics 123 Lab #5 Telescope: Ends 27 th In this lab, you will construct a simple telescope using two lenses. Mount the source (illuminated arrow) and the screen on the optical bench, and mount one of the lenses between them. Adjust their positions until a real image of the arrow is focused on the screen. For best results, adjust the positions so that the lens is about half-way between the object and the image. Measure p and q. Calculate f from the thin lens equation, Repeat for the other lens. Record your results below. Construct a telescope by mounting the two lenses a distance f 1 + f 2 apart. Use the lens with the smaller focal length for the eyepiece. View the large scale mounted on the wall across the room. The distance between the two lenses may be adjusted to bring the image into better focus. Measure the angular magnification m of the telescope by viewing the scale through the telescope with one eye and looking directly at the scale with the other eye. In this way, you ought to be able to see both the magnified and unmagnified scale superimposed on each other. Finally, calculate m from the measured focal lengths.

10 Fig 35-4, p.1098

11 Fig 37-1a, p.1178

12 p.1178

13 Fig 37-1b, p.1178

14 Turn the laser on through 2 slits. What do we see?

15 p.1108

16 Fig 35-17a, p.1108

17 Fig 37-3, p.1179

18 Fig 37-2a, p.1179

19 Fig 37-4, p.1179

20 Fig 37-4a, p.1179

21 Fig 37-4b, p.1179

22 Fig 37-4c, p.1179

23 Fig 37-3, p.1179

24 Time For Active Figure What happens if we decrease d?

25 I am going to move the slits in the pattern further apart. What will happen to the number of the nodal lines? A.Increase B.Decrease

26 Consider the interference pattern produced by shining light through a double slit. For which color will the bright spots in the pattern be further apart? A.blue B.red C.neither

27 Time For Active Figure Again What happens if we decrease λ? & now math

28 Fig 37-5a, p.1180

29 Fig 37-5b, p.1180

30 Multiple Slits

31 Physics 123 Lab #6 Diffraction Grating In this lab, you will observe the interference pattern produced by shining a laser beam through a diffraction grating. From the distance between peaks in the pattern, you will determine the distance between the slits in the grating. The He-Ne laser used in this lab produces red light of wavelength 633 nm. Turn on the laser. Its beam should pass through the diffraction grating. You should observe the interference pattern on the wall. Use a meter stick to measure the distance Δx between peaks in the interference pattern. Average this distance over several adjacent peaks so that your measurement will be as accurate as possible. Record your result below. Use the tape measure to determine the distance L between the diffraction grating and the interference pattern on the wall and record your result below. Calculate the angle θ between adjacent bright spots in the interference pattern and record your result below. Using d sin θ = λ = 633 nm, calculate the distance d between the slits in the grating and record your result below. DUE Friday 3 June

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