meanings of Wavelength definition of Wavelength books about Wavelength references on Wavelength articles about Wavelength web search for Wavelength dreams about Wavelength
 Wavelength - Definition 

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:

Image:Wavelength.png

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, for signals (waves) in air, this is the speed of sound in air. The relationship is given by:

<math>

\lambda = \frac{c}{f} <math> where:

λ = wavelength of a sound wave or electromagnetic wave
c = speed of light in vacuum = 299,792.458 km/s ~ 300 000 km/s = 300,000,000 m/s or
c = speed of sound in air = 343 m/s at 20 °C (68 °F)
f = frequency of the wave

For radio waves this relationship is approximated with the formula: wavelength (in metres) = 300 / frequency (in megahertz).

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 but the frequey of the wave is unchanged. The wavelength of the wave in the medium, λ' is given by:

<math>

\lambda^\prime = \frac{\lambda_0}{n} <math> where:

λ0 is the vacuum wavelength of the wave

Wavelengths of electromagnetic radiation, no matter what medium they are travelling through, are uslly 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

<math>

\lambda = \frac{h}{p} = \frac {h}{{m}{v}} \sqrt{1 - \frac{v^2}{c^2}} <math> where:

h is Planck's constant
p is the particle's momentum
m is the particle's mass
v is the particle's velocity

The greater the energy, the larger the frequency and the shorter (smaller) the wavelength. Given te relationship between wavelength and frequency, it follows that short wavelengths are more energetic than long wavelengths.

See Also

Waves

frequency, period, amplitude

External link




da:Bølgelængde de:Wellenlänge es:Longitud de onda fr:Longueur d'onde is:Bylgjulengd it:Lunghezza d'onda nl:Golflengte ja:波長 nds:Bülgenläng pl:Długość fali pt:Comprimento de onda sl:Valovna dolžina sv:Våglängd

Copyright 2008 WordIQ.com - Privacy Policy  ::  Terms of Use  :: Contact Us  :: About Us
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Wavelength".