Wavelength of a sine wave.

In a wave, properties vary with position. For example, in a sound wave the air pressure oscillates, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary.

Visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm (430–750 THz). For other examples, see electromagnetic spectrum. The wavelengths of sound frequencies audible to the human ear (20 Hz–20 kHz) are between approximately 17 m and 17 mm, respectively. So the wavelengths in audible sound are much longer than those in visible light.

Speed=wavelengh×frequency