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Photograph of a triangular prism, dispersing light Lamps as seen through a prism. In optics, a dispersive prism is an optical prism that is used to disperse light, that is, to separate light into its spectral components (the colors of the rainbow). Different wavelengths (colors) of light will be deflected by the prism at different angles. [1]
This is generally an unwanted effect of dispersive prisms. In some cases this can be avoided by choosing prism geometry which light enters and exits under perpendicular angle, by compensation through non-planar light trajectory, or by use of p-polarized light. Total internal reflection alters only the mutual phase between s- and p-polarized light.
In a dispersive prism, material dispersion (a wavelength-dependent refractive index) causes different colors to refract at different angles, splitting white light into a spectrum. A compact fluorescent lamp seen through an Amici prism. Dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. [1]
Rainbows are formed by dispersion of light, in which the refraction angle depends on the light's frequency. Refraction is also responsible for rainbows and for the splitting of white light into a rainbow-spectrum as it passes through a glass prism. Glass and water have higher refractive indexes than air.
The result is that red light is bent less sharply than violet as it passes through the prism, creating a spectrum of colors. Newton's observation of prismatic colors (David Brewster 1855) Newton originally divided the spectrum into six named colors: red, orange, yellow, green, blue, and violet.
A transparent object allows light to transmit or pass through. Conversely, an opaque object does not allow light to transmit through and instead reflecting or absorbing the light it receives. Most objects do not reflect or transmit light specularly and to some degree scatters the incoming light, which is called glossiness.
The aligned light then passes through the prism in which it is refracted twice (once when entering and once when leaving). Due to the nature of a dispersive element the angle with which light is refracted depends on its wavelength. This leads to a spectrum of thin lines of light, each being observable at a different angle.
It is possible to make the effective speed of light dependent on wavelength by making light pass through a material which has a non-constant index of refraction, or by using light in a non-uniform medium such as a waveguide. In this case, the waveform will spread over time, such that a narrow pulse will become an extended pulse, i.e., be dispersed.