The distance between two points on a wave which have the same value and the same rate of change of the value of a parameter, for example, electric intensity, characterizing the wave. The wavelength, usually designated by the Greek letter λ, is equal to the speed of propagation c of the wave divided by the frequency of vibration f; that is, λ = (see illustration). See also: Wave (physics)
The wavelength for a sound of a given frequency varies greatly, depending upon the speed of propagation in the medium in which the sound is moving. For example, a sound wave having a frequency of 1000 Hz would have a wavelength of approximately 1 ft (0.3 m) in air, 412 ft (1.3 m) in water, and 17 ft (5.1 m) in steel. The wavelength of electromagnetic waves depends on the velocity of light in the material in which the waves are traveling. See also: Wave motion