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
λ has an inverse relationship to
frequency f, 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, dealing with signals (waves) in air we have the
speed of sound in air, so the conversion becomes,\n:\nwhere:
- λ = wavelength of an electromagnetic wave or\n*λ = wavelength of a sound wave \n*c = speed of light in vacuum = 299,792.458 km/s ~ 300,000 km/s = 300,000,000 m/s or\n*c = speed of sound in air = 343 m/s at 20 °C (68 °F)\n*f = frequency of the wave
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:\n:\nwhere λ
0 is the vacuum wavelength of the wave.\nWavelengths 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\n:\nwhere
h is the
Planck constant,
p is the particle's momentum,
m is the particle's
mass, and
v is the particle's velocity.
The greater the energy, the larger the frequency and the shorter (smaller) the wavelength. Given the relationship between wavelength and frequency, it follows that short wavelengths are more energetic than long wavelengths.
See also:
frequency,
period,
amplitude
External link
\n*Conversion: Wavelength to Frequency and back
Category:Physical quantity
\n \n \n\n \n\n\nnds:Bülgenläng\n \n\n\n\n
