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2. Resources Resources Chapter Presentation Visual Concepts Sample Problems Transparencies Standardized Test Prep

3. Chapter 15 Interference and Diffraction Table of Contents Section 1 Interference Section 2 Diffraction Section 3 Lasers

4. Section 1 Interference Chapter 15 Objectives • Describehow light waves interfere with each other to produce bright and dark fringes. • Identifythe conditions required for interference to occur. • Predictthe location of interference fringes using the equation for double-slit interference.

5. Section 1 Interference Chapter 15 Combining Light Waves • Interference takes place only between waves with the same wavelength. A light source that has a single wavelength is called monochromatic. • Inconstructive interference,component waves combine to form a resultant wave with the same wavelength but with an amplitude that is greater than the either of the individual component waves. • In the case ofdestructive interference,the resultant amplitude is less than the amplitude of the larger component wave.

6. Section 1 Interference Chapter 15 Interference Between Transverse Waves

7. Section 1 Interference Chapter 15 Combining Light Waves, continued • Waves must have a constant phase difference for interference to be observed. • Coherenceis the correlation between the phases of two or more waves. • Sources of light for which the phase difference is constant are said to be coherent. • Sources of light for which the phase difference is not constant are said to be incoherent.

8. Section 3 Lasers Chapter 15 Incoherent and Coherent Light

9. Section 1 Interference Chapter 15 Combining Light Waves

10. Section 1 Interference Chapter 15 Demonstrating Interference • Interference can be demonstrated by passing light through two narrow parallel slits. • If monochromatic light is used, the light from the two slits produces a series of bright and dark parallel bands, orfringes,on a viewing screen.

11. Section 1 Interference Chapter 15 Conditions for Interference of Light Waves

12. Section 1 Interference Chapter 15 Demonstrating Interference, continued • The location of interference fringes can be predicted. • Thepath differenceis the difference in the distance traveled by two beams when they are scattered in the same direction from different points. • The path difference equals dsinq.

13. Section 1 Interference Chapter 15 Interference Arising from Two Slits

14. Section 2 Diffraction Chapter 15 Objectives • Describehow light waves bend around obstacles and produce bright and dark fringes. • Calculatethe positions of fringes for a diffraction grating. • Describehow diffraction determines an optical instrument’s ability to resolve images.

15. Section 2 Diffraction Chapter 15 The Bending of Light Waves • Diffraction isa change in the direction of a wave when the wave encounters an obstacle, an opening, or an edge. • Light waves form adiffraction patternby passing around an obstacle or bending through a slit and interfering with each other. • Wavelets (as in Huygens’ principle) in a wave front interfere with each other.

16. Section 2 Diffraction Chapter 15 Destructive Interference in Single-Slit Diffraction

17. Section 2 Diffraction Chapter 15 The Bending of Light Waves, continued • In a diffraction pattern, the central maximum is twice as wide as the secondary maxima. • Light diffracted by an obstacle also produces a pattern.

18. Section 2 Diffraction Chapter 15 Function of a Spectrometer

19. Section 2 Diffraction Chapter 15 Resolution of Two Light Sources

20. Section 3 Lasers Chapter 15 Objectives • Describethe properties of laser light. • Explainhow laser light has particular advantages in certain applications.

21. Section 3 Lasers Chapter 15 Lasers and Coherence • Alaseris a device that produces coherent light at a single wavelength. • The word laser is an acronym of “light amplification by stimulated emission of radiation.” • Lasers transform other forms of energy into coherent light.

22. Section 3 Lasers Chapter 15 Comparing Incoherent and Coherent Light

23. Section 3 Lasers Chapter 15 Laser

24. Section 3 Lasers Chapter 15 Applications of Lasers • Lasers are used to measure distances with great precision. • Compact disc and DVD players use lasers to read digital data on these discs. • Lasers have many applications in medicine. • Eye surgery • Tumor removal • Scar removal

25. Section 3 Lasers Chapter 15 Components of a Compact Disc Player

26. Chapter 15 Standardized Test Prep Multiple Choice 1. In the equations for interference, what does the term d represent? A. the distance from the midpoint between the two slits to the viewing screen B. the distance between the two slits through which a light wave passes C. the distance between two bright interference fringes D. the distance between two dark interference fringes

27. Chapter 15 Standardized Test Prep Multiple Choice, continued 1. In the equations for interference, what does the term d represent? A. the distance from the midpoint between the two slits to the viewing screen B. the distance between the two slits through which a light wave passes C. the distance between two bright interference fringes D. the distance between two dark interference fringes

28. Chapter 15 Standardized Test Prep Multiple Choice, continued 2. Which of the following must be true for two waves with identical amplitudes and wavelengths to undergo complete destructive interference? F. The waves must be in phase at all times. G. The waves must be 90º out of phase at all times. H. The waves must be 180º out of phase at all times. J. The waves must be 270º out of phase at all times.

29. Chapter 15 Standardized Test Prep Multiple Choice, continued 2. Which of the following must be true for two waves with identical amplitudes and wavelengths to undergo complete destructive interference? F. The waves must be in phase at all times. G. The waves must be 90º out of phase at all times. H. The waves must be 180º out of phase at all times. J. The waves must be 270º out of phase at all times.

30. Chapter 15 Standardized Test Prep Multiple Choice, continued 3. Which equation correctly describes the condition for observing the third dark fringe in an interference pattern? A.dsin q = l/2 B.dsin q = 3l/2 C.dsin q = 5l/2 D.dsin q = 3l

31. Chapter 15 Standardized Test Prep Multiple Choice, continued 3. Which equation correctly describes the condition for observing the third dark fringe in an interference pattern? A.dsin q = l/2 B. dsin q = 3l/2 C.dsin q = 5l/2 D.dsin q = 3l

32. Chapter 15 Standardized Test Prep Multiple Choice, continued 4. Why is the diffraction of sound easier to observe than the diffraction of visible light? F. Sound waves are easier to detect than visible light waves. G. Sound waves have longer wavelengths than visible light waves and so bend more around barriers. H. Sound waves are longitudinal waves, which diffract more than transverse waves. J. Sound waves have greater amplitude than visible light waves.

33. Chapter 15 Standardized Test Prep Multiple Choice, continued 4. Why is the diffraction of sound easier to observe than the diffraction of visible light? F. Sound waves are easier to detect than visible light waves. G. Sound waves have longer wavelengths than visible light waves and so bend more around barriers. H. Sound waves are longitudinal waves, which diffract more than transverse waves. J. Sound waves have greater amplitude than visible light waves.

34. Chapter 15 Standardized Test Prep Multiple Choice, continued 5. Monochromatic infrared waves with a wavelength of 750 nm pass through two narrow slits. If the slits are 25 µm apart, at what angle will the fourth order bright fringe appear on a viewing screen? A. 4.3º B. 6.0º C. 6.9º D. 7.8º

35. Chapter 15 Standardized Test Prep Multiple Choice, continued 5. Monochromatic infrared waves with a wavelength of 750 nm pass through two narrow slits. If the slits are 25 µm apart, at what angle will the fourth order bright fringe appear on a viewing screen? A. 4.3º B. 6.0º C. 6.9º D. 7.8º

36. Chapter 15 Standardized Test Prep Multiple Choice, continued 6. Monochromatic light with a wavelength of 640 nm passes through a diffraction grating that has 5.0  104 lines/m. A bright line on a screen appears at an angle of 11.1º from the central bright fringe.What is the order of this bright line? F.m = 2 G.m = 4 H.m = 6 J.m = 8

37. Chapter 15 Standardized Test Prep Multiple Choice, continued 6. Monochromatic light with a wavelength of 640 nm passes through a diffraction grating that has 5.0  104 lines/m. A bright line on a screen appears at an angle of 11.1º from the central bright fringe.What is the order of this bright line? F.m = 2 G.m = 4 H.m = 6 J.m = 8

38. Chapter 15 Standardized Test Prep Multiple Choice, continued 7. For observing the same object, how many times better is the resolution of the telescope shown on the left in the figure below than that of the telescope shown on the right? A. 4 B. 2 C. 1/2 D. 1/4

39. Chapter 15 Standardized Test Prep Multiple Choice, continued 7. For observing the same object, how many times better is the resolution of the telescope shown on the left in the figure below than that of the telescope shown on the right? A. 4 B. 2 C. 1/2 D. 1/4

40. Chapter 15 Standardized Test Prep Multiple Choice, continued 8. What steps should you employ to design a telescope with a high degree of resolution? F. Widen the aperture, or design the telescope to detect light of short wavelength. G. Narrow the aperture, or design the telescope to detect light of short wavelength. H. Widen the aperture, or design the telescope to detect light of long wavelength. J. Narrow the aperture, or design the telescope to detect light of long wavelength.

41. Chapter 15 Standardized Test Prep Multiple Choice, continued 8. What steps should you employ to design a telescope with a high degree of resolution? F. Widen the aperture, or design the telescope to detect light of short wavelength. G. Narrow the aperture, or design the telescope to detect light of short wavelength. H. Widen the aperture, or design the telescope to detect light of long wavelength. J. Narrow the aperture, or design the telescope to detect light of long wavelength.

42. Chapter 15 Standardized Test Prep Multiple Choice, continued 9. What is the property of a laser called that causes coherent light to be emitted? A. population inversion B. light amplification C. monochromaticity D. stimulated emission

43. Chapter 15 Standardized Test Prep Multiple Choice, continued 9. What is the property of a laser called that causes coherent light to be emitted? A. population inversion B. light amplification C. monochromaticity D. stimulated emission

44. Chapter 15 Standardized Test Prep Multiple Choice, continued 10. Which of the following is not an essential component of a laser? F. a partially transparent mirror G. a fully reflecting mirror H. a converging lens J. an active medium

45. Chapter 15 Standardized Test Prep Multiple Choice, continued 10. Which of the following is not an essential component of a laser? F. a partially transparent mirror G. a fully reflecting mirror H. a converging lens J. an active medium

46. Chapter 15 Standardized Test Prep Short Response 11. Why is laser light useful for the purposes of making astronomical measurements and surveying?

47. Chapter 15 Standardized Test Prep Short Response, continued 11. Why is laser light useful for the purposes of making astronomical measurements and surveying? Answer: The beam does not spread out much or lose intensity over long distances.

48. Chapter 15 Standardized Test Prep Short Response, continued 12. A diffraction grating used in a spectrometer causes the third-order maximum of blue light with a wavelength of 490 nm to form at an angle of 6.33º from the central maximum (m = 0). What is the separation between the lines of the grating?

49. Chapter 15 Standardized Test Prep Short Response, continued 12. A diffraction grating used in a spectrometer causes the third-order maximum of blue light with a wavelength of 490 nm to form at an angle of 6.33º from the central maximum (m = 0). What is the separation between the lines of the grating? Answer: 7.5 104 lines/m = 750 lines/cm

50. Chapter 15 Standardized Test Prep Short Response, continued 13. Telescopes that orbit Earth provide better images of distant objects because orbiting telescopes are more able to operate near their theoretical resolution than telescopes on Earth. The orbiting telescopes needed to provide high resolution in the visible part of the spectrum are much larger than the orbiting telescopes that provide similar images in the ultraviolet and X-ray portion of the spectrum. Explain why the sizes must vary.