Chapter 17: Q6. (page 483)
FIGURE EX17.6 shows a standing wave on a 2.0-m-long string that has been fixed at both ends and tightened until the wave speed is 40 m/s. What is the frequency?
40Hz
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A soap bubble is essentially a very thin film of water 1n = 1.332 surrounded by air. The colors that you see in soap bubbles are produced by interference.
a. Derive an expression for the wavelengths lC for which constructive interference causes a strong reflection from a soap bubble of thickness d. Hint: Think about the reflection phase shifts at both boundaries.
b. What visible wavelengths of light are strongly reflected from a 390-nm-thick soap bubble? What color would such a soap bubble appear to be?
a. What are the three longest wavelengths for standing waves on a 240-cm-long string that is fixed at both ends? b. If the frequency of the second-longest wavelength is 50 Hz, what is the frequency of the third-longest wavelength?
FIGURE EX17.2 is a snapshot graph at t = 0 s of two waves approaching each other at 1.0 m/s. Draw six snapshot graphs, stacked vertically, showing the string at 1 s intervals from t = 1 s to t = 6 s.
The 40-cm-long tube of FIGURE P17.54 has a 40-cm-long insert
that can be pulled in and out. A vibrating tuning fork is held next to the
tube. As the insert is slowly pulled out, the sound from the tuning fork
creates standing waves in the tube when the total length L is 42.5 cm, 56.7 cm, and 70.9 cm. What is the frequency of the tuning fork? Assume vsound = 343 m/s.
Engineers are testing a new thin-film coating whose index of refraction is less than that of glass. They deposit a 560-nm-thick layer on glass, then shine lasers on it. A red laser with a wavelength of 640 nm has no reflection at all, but a violet laser with a wavelength of 400 nm has a maximum reflection. How the coating behaves at other wavelengths is unknown. What is the coating’s index of refraction?
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