A vibrating tuning fork is held over a water column with one end closed and the other open. As the water level is allowed to fall, a loud sound is heard for water levels separated by 17 cm. If the speed of sound in air is 340 m/s, the frequency of the tuning fork is:
A) 500 Hz
B) 1000 Hz
C) 2000 Hz
D) 5780 Hz
E) 578,000 Hz

Question

Quizplus · Accepted Answer

The wavelength of the sound wave produced by the tuning fork is equal to twice the distance between consecutive loud sounds heard from the water column (since the closed end of the column creates a node for the wave, so the open end is effectively the antinode):

λ = 2d = 2(17 cm) = 34 cm = 0.34 m

The speed of sound in air is given as 340 m/s, which is equal to the product of wavelength and frequency:

v = λf

Rearranging this equation, we can solve for the frequency:

f = v/λ = (340 m/s)/(0.34 m) = 1000 Hz

So the frequency of the tuning fork is 1000 Hz, which corresponds to choice B.

A Vibrating Tuning Fork Is Held Over a Water Column