Wave Speed

56. A student reading his physics book on a lake dock notices that the distance between two incoming wave crests is about 2.4 m, and then measures the time of arrival between wave crests to be 1.6 s. What is the approximate speed of the waves?

57. Light waves travel in a vacuum at a speed of 300,000 km/s. The frequency of visible light is about 10¹⁴ Hz. What is the approximate wavelength of the light?

59. The range of sound audible to the human ear has frequencies from about 20 Hz to 20 kHz. If the speed of sound in air is 345 m/s, what are the limits of this audible range in wavelengths?

61. A sonar generator on a submarine produces periodic ultrasonic waves at a frequency of 2.50 MHz. The wavelength of the waves in sea water is 4.80 X 10^-4 m. When the generator is directed downward, an echo reflected from the ocean floor is received 16.7 s later. How deep is the ocean at that point? (Assume wavelength is constant at all depths.)

62. In watching a transverse wave go by, a person notes that 13 crests go by in a time of 3.0 s. If the distance between two successive crests is measured to be 0.75 m, what is the speed of the wave?

63. A wave traveling in the +x direction is shown in 13.25a. The particle displacement at a particular location in the medium through which the wave travels is shown in Fig. 13.25b. (a) What is the amplitude of the traveling wave? (b) What is the wave speed?

FIGURE 13.25 How high and how fast?
Exercise 63.

64. A wave with a frequency of 60 Hz has a speed of 12 m/s in a particular medium. (a) What is the wavelength? (b) If the wave is transmitted into another medium in which it is propagated at a speed of 20 m/s, by how much will the wavelength change? (The frequency remains the same.)