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Double-slit interference Diffraction gratings Thin-film interference Single-slit diffraction

Chapter 17 Wave Optics. Topics:. Double-slit interference Diffraction gratings Thin-film interference Single-slit diffraction Circular-aperture diffraction. Sample question:.

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Double-slit interference Diffraction gratings Thin-film interference Single-slit diffraction

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  1. Chapter 17 Wave Optics Topics: • Double-slit interference • Diffraction gratings • Thin-film interference • Single-slit diffraction • Circular-aperture diffraction Sample question: The vivid colors of this hummingbird’s feathers have a sheen unlike that of ordinary pigments, and they change subtly depending on the angle at which they’re viewed. How does light interact with the feathers to produce this bright display? Slide 17-1

  2. Reading Quiz • All waves spread out after passing through a small enough gap in a barrier. This phenomenon is known as • antireflection • double-slit interference • refraction • diffraction Slide 17-2

  3. Answer • All waves spread out after passing through a small enough gap in a barrier. This phenomenon is known as • diffraction Slide 17-3

  4. Reading Quiz • The wave model of light is needed to explain many of the phenomena discussed in this chapter. Which of the following can be understood without appealing to the wave model? • single-slit diffraction • thin-film interference • sharp-ended shadows • double-slit interference Slide 17-4

  5. Answer • The wave model of light is needed to explain many of the phenomena discussed in this chapter. Which of the following can be understood without appealing to the wave model? • sharp-ended shadows Slide 17-5

  6. Water Waves Spread Out behind a Small Opening Slide 17-6

  7. Light Waves Also Spread Out Behind a Very Narrow Slit Slide 17-7

  8. Young’s Double-Slit Interference Experiment Slide 17-8

  9. Analyzing the Double-Slit Experiment Slide 17-9

  10. Bright and Dark Fringes in the Double-Slit Experiment Slide 17-10

  11. Example • Two narrow slits 0.04 mm apart are illuminated by light from a HeNe laser (λ = 633 nm). • What is the angle of the first (m = 1) bright fringe? • What is the angle of the thirtieth bright fringe? Slide 17-11

  12. The Diffraction Grating Slide 17-12

  13. Bright Fringes for a Diffraction Grating Slide 17-13

  14. The Intensity Pattern Due to a Diffraction Grating Slide 17-14

  15. The Fringes Become Very Narrow as the Number of Slits is Increased Slide 17-15

  16. A Diffraction Grating Splits Light into the Wavelengths That Make It Up Slide 17-16

  17. Thin-Film Interference Slide 17-17

  18. Phase Changes Due to Reflection Slide 17-18

  19. Analyzing Thin-Film Interference Slide 17-19

  20. Slide 17-20

  21. Checking Understanding • A film of oil (noil = 1.2) floats on top of an unknown fluid “X” (with unknown index of refraction nx). The thickness of the oil film is known to be very small, on the order of 10 nm. A beam of white light illuminates the oil from the top, and you observe that there is very little reflected light, much less reflection than at an interface between air and X. What can you say about the index of refraction of X? • nx > 1.2 • nx < 1.2 • nx = 1.2 • There is insufficient information to tell. Slide 17-21

  22. Answer • A film of oil (noil = 1.2) floats on top of an unknown fluid “X” (with unknown index of refraction nx). The thickness of the oil film is known to be very small, on the order of 10 nm. A beam of white light illuminates the oil from the top, and you observe that there is very little reflected light, much less reflection than at an interface between air and X. What can you say about the index of refraction of X? • nx < 1.2 Slide 17-22

  23. Single-Slit Diffraction Light passing through a narrow slit spreads out beyond the slit. Slide 17-23

  24. Analyzing Single-Slit Diffraction Slide 17-24

  25. Single-Slit Diffraction: Positions and Intensities Slide 17-25

  26. Circular-Aperture Diffraction Slide 17-26

  27. Checking Understanding • The fringe pattern below could be due to • a single slit or two slits. • ten slits. • either two slits or ten slits. • either one slit or two slits. Slide 17-27

  28. Answer • The fringe pattern below could be due to • ten slits. Slide 17-28

  29. Checking Understanding • If the two slits shown are illuminated in turn by a broad laser beam, which produces a wider illuminated region on the screen at the right? • The 1-cm-wide slit. • The 2-cm-wide slit. • There’s no way to tell with the information given. Slide 17-29

  30. Answer • If the two slits shown are illuminated in turn by a broad laser beam, which produces a wider illuminated region on the screen at the right? • There’s no way to tell with the information given. Slide 17-29

  31. Exercise What is the diameter of an aperture for which the diffraction central maximum is the same size as the geometric image of the hole? Slide 17-31

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