Wavelength
The wavelength is the distance between repeating units of a wave pattern. It is commonly designated by the greek letter lambda (λ).
In a sine wave, the wavelength is the distance between peaks:
The x axis represents distance, and I would be some varying quantity (for instance air pressure for a sound wave or strength of the electric or magnetic field for light), at a given point in time as a function of x.
Wavelength has an inverse relationship frequency, the number of peaks to pass a point in a given time. The wavelength is equal to the speed of the wave divided by the frequency of the wave. When dealing with electromagnetic radiation in a vacuum, this speed is the speed of light c, so the conversion becomes,
where:
For radio waves this relationship is easily handled with this formula: meters of wavelength = 300/frequency in megahertz (MHz)
When light waves (and other electromagnetic waves) enter a medium, their wavelength is reduced by a factor equal to the refractive index n of the medium, but the frequency of the wave is unchanged. The wavelength of the wave in the medium, λ' is given by:
where λ0 is the vacuum wavelength of the wave.
Wavelengths of electromagnetic radiation are usually quoted in terms of the vacuum wavelength, although this is not always explicitly stated.
Louis-Victor de Broglie discovered that all particles with momentum have a wavelength, called the de Broglie wavelength. For a relativistic particle, this wavelength is given by
where h is the Planck constant, p is the particle's momentum, m is the particle's mass, and v is the particle's velocity.
See also: frequency, period, amplitude
Wavelength is the title of a 1978 album by Van Morrison.
Referenced By
Letters used in Maths and Science | List of astronomical topics | List of astronomical topics (N-Z) | List of electronics | List of electronics topics | List of letters used in mathematics and science | List of physics topics R-Z | Wavenumber
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