# Wavelength

Longitudinal wave: the distance from the start of one compression or rarefaction to the start of the next compression or rarefaction at an instant of time.

Shear wave: the distance between successive peaks in the perpendicular motion of the particles of the medium at an instant of time.

The shortest repetition length for a periodic wave. For example, it is the distance from crest to crest or from trough to trough. In compressional waves, such as sound waves, it is the measurement of the distance from rarefaction to rarefaction, or compression to compression.

The wavelength of visible light lies in the range 400nm to 700nm.

The wavelength of audio waves in air lie in the range 0.017m to 17m (20Hz to 20kHz).

In all wave motion the shorter the wavelength, the greater the energy carried by the wave.

Wavelength, λ

where

c = wave speed [ms-1]
f = frequency [Hz]
k = wavenumber [m-1]

 Violet (visible light) 4x10-7m Red (visible light) 7x10-7m 20kHz audio waves 0.017m VHF radio waves 1 to 10m 20Hz audio waves 17m VLF radio waves 10km to 100km

Subjects: Noise & Vibration Physics