Wave practice problems

Wave questions I

1.  Differentiate between mechanical and electromagnetic waves.  Give examples.

2.  Draw a wave and identify the primary parts (wavelength, crest, trough, amplitude).

3.  Find the speed of a 500 Hz wave with a wavelength of 0.25 m.

4.  What is the frequency of a wave that travels at 24 m/s, if 3 full waves fit in a 12-m space?  (Hint:  find the wavelength first.)

5.  Approximately how much greater is the speed of light than the speed of sound?

6.  Show how to compute the wavelength of WTMD's signal (89.7 MHz).  Note that MHz means 'million Hz."  Recall that radio waves travel at the speed of light.

7.  Middle C vibrates at 262 Hz (approximately).  Find the frequencies of the next 2 C's (1 and 2 octaves above this one).

Answers:

1/2.  See notes

3.  v = f l = 500(0.25) = 125 m/s

4.  wavelength (l) = 12/3 = 4 m

v = f l

24 = f (4)

f = 6 Hz

5.  300,000,000 / 340 = approx one million times greater

6.  v = f l

300,000,000 = (89,700,000) l

l = 300,000,000/89,700,000

7.  In music, octaves are found by doubling the frequency of the first note.

524 Hz, 1048 Hz