A wave x meters long has a speed of y meters per second. The frequency of the wave is

a. x/y hertz

c. y · x hertz

b. y/x hertz

d. y + x hertz

The answer is B. y/x hertz.

Frequency of a wave is defined as the ratio between the speed and wavelength of the wave. The unit of frequency is hertz (Hz) which is also equivalent to s^-1 or "per second". Following the units of wavelength (m) and speed (m/s), it can also be inferred that frequency is equal to (m/s) / m or y/x.