Wavelength
From Halbeeg, the open encyclopedia · Af-Soomaali
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Wavelength is the distance between two consecutive points on a wave that are in the same state of oscillation—for example, two adjacent crests or two adjacent troughs. It is usually denoted by the Greek letter lambda (λ). The standard unit of measurement is the metre, but depending on the wavelength, nanometres (nm), centimetres, or larger multiples of metres are also used.
Wavelength is one of three fundamental parameters that define a wave, the other two being frequency (f) and wave speed (v). The relationship between them is v = f λ. This means that when wave speed remains constant, wavelength and frequency are inversely proportional: an increase in one causes a decrease in the other.
Definition and measurement
For a regularly oscillating wave, wavelength is the spatial period—the distance over which the wave pattern repeats itself. Waves that are not purely sinusoidal can be decomposed into components (Fourier analysis), each with its own wavelength. There is also the wavenumber, which is the reciprocal of wavelength, k = 2π/λ, useful in wave mathematics.
Media and changes
When a wave passes from one medium into another—for example, light from air into water—its frequency remains constant, but its speed changes, and therefore its wavelength changes. This is one of the reasons light bends when entering a different medium (refraction). The Doppler effect also plays a role: when the wave source and observer move relative to each other, the observed wavelength increases or decreases.
Types of waves
Electromagnetic waves are classified by their wavelengths: gamma rays and X-rays have extremely short wavelengths, visible light has wavelengths in the range of hundreds of nanometres, while radio waves can reach from metres to kilometres. Sound waves are mechanical waves that travel through air, and their wavelength depends on the frequency of the sound and the speed of sound in the medium.
In quantum physics, matter is associated with a wavelength (the de Broglie wavelength) that is inversely related to the momentum of the object. This idea underlies the description of the wave-particle duality of matter at the microscopic scale.