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Unformatted text preview: Chapter 24 Additional Example Problems w/Solutions Q1. A laser beam ( = 632.8 nm) is incident on two slits 0.200 mm apart. How far apart are the bright interference fringes on a screen 5.00 m away from the double slits? Ans: ( 29 1 1 bright m m L L L y y y m m d d d + =- = +- = ( 29 ( 29 9 2 3 632.8 10 m 5.00 m 1.58 10 m 0.200 10 m--- = = = 1.58 cm Q2. A Youngs interference experiment is performed with blue-green argon laser light. The separation between the slits is 0.500 mm, and the interference pattern on a screen 3.30 m away shows the first maximum 3.40 mm from the center of the pattern. What is the wavelength of argon laser light? Ans: Since the screen distance from the central maximum to the maximum of order m is bright L y m d = , the wavelength is given by ( 29 ( 29 ( 29( 29 3 3 7 3.40 10 m 0.500 10 m 5.15 10 m 1 3.30 m m y d m L --- = = = = 515 nm Q3. A thin film of oil ( n = 1.25) is located on a smooth, wet pavement. When viewed perpendicular to the pavement, the film appears to be predominantly red (640 nm) and has no blue color (512 nm). How thick is the oil film? Ans: Since air oil water n n n < < , light reflected from both top and bottom surfaces of the oil film experiences phase reversal, resulting in zero net phase difference due to reflections. The condition for constructive interference is ( 29 2 n oil t m m n = = , so the thicknesses that produce constructive interference for 640 nm light are ( 29 640 nm...
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- Summer '08