Wavelength
![Wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests, or troughs, or corresponding zero crossings as shown.](/Images/godic/202412/21/Sine_wavelength.svg1743.png")
![Sinusoidal standing waves in a box that constrains the end points to be nodes will have an integer number of half wavelengths fitting in the box.](/Images/godic/202412/21/Waves_in_Box.svg1743.png")
![Refraction: upon entering a medium where its speed is lower, the wave changes direction.](/Images/godic/202412/21/Refraction_-_Huygens-Fresnel_principle.svg1743.png")
![Separation of colors by a prism (click for animation)](/Images/godic/202412/21/Light_dispersion_conceptual_waves1743.gif")
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats, and the inverse of the spatial frequency. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.