What physics law describes how light acts as a prism?

I thought a prism was a triangular glass piece. How can light act as a prism. Unless you're referring to the rainbow effect, whose scientific name I can't recall. 

This article is about optical prisms. For the geometric shape, see Prism (geometry). For other uses, see Prism (disambiguation).
"Prismatic" redirects here. For other uses, see Prismatic (disambiguation).
A plastic prism

In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use "prism" usually refers to this type. Some types of optical prism are not in fact in the shape of geometric prisms. Prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, plastic and fluorite.

A dispersive prism can be used to break light up into its constituent spectral colors (the colors of the rainbow). Furthermore, prisms can be used to reflect light, or to split light into components with different polarizations.


hmmm.... still no definition of what you want.....

This post was edited by WM BARR . =ABSOLUTE TRASH at August 15, 2017 1:21 AM MDT

Okay, I'll try this one....


Dispersion of Light by Prisms

Dispersion of Light by Prisms
Rainbow Formation
Mirages

In the Light and Color unit of The Physics Classroom Tutorial, the visible light spectrum was introduced and discussed. Visible light, also known as white light, consists of a collection of component colors. These colors are often observed as light passes through a triangular prism. Upon passage through the prism, the white light is separated into its component colors - red, orange, yellow, green, blue and violet. The separation of visible light into its different colors is known as dispersion. It was mentioned in the Light and Color unit that each color is characteristic of a distinct wave frequency; and different frequencies of light waves will bend varying amounts upon passage through a prism. In this unit, we will investigate the dispersion of light in more detail, pondering the reasons why different frequencies of light bend or refract different amounts when passing through the prism.

Earlier in this unit, the concept of optical density was introduced. Different materials are distinguished from each other by their different optical densities. The optical density is simply a measure of the tendency of a material to slow down light as it travels through it. As mentioned earlier, a light wave traveling through a transparent material interacts with the atoms of that material. When a light wave impinges upon an atom of the material, it is absorbed by that atom. The absorbed energy causes the electrons in the atom to vibrate. If the frequency of the light wave does not match the resonance frequency of the vibrating electrons, then the light will be reemitted by the atom at the same frequency at which it impinged upon it. The light wave then travels through the interatomic vacuum towards the next atom of the material. Once it impinges upon the next atom, the process of absorption and re-emission is repeated.




The optical density of a material is the result of the tendency of the atoms of a material to maintain the absorbed energy of the light wave in the form of vibrating electrons before reemitting it as a new electromagnetic disturbance. Thus, while a light wave travels through a vacuum at a speed of c (3.00 x 108 m/s), it travels through a transparent material at speeds less than c. The index of refraction value (n) provides a quantitative expression of the optical density of a given medium. Materials with higher index of refraction values have a tendency to hold onto the absorbed light energy for greater lengths of time before reemitting it to the interatomic void. The more closely that the frequency of the light wave matches the resonant frequency of the electrons of the atoms of a material, the greater the optical density and the greater the index of refraction. A light wave would be slowed down to a greater extent when passing through such a material

What was not mentioned earlier in this unit is that the index of refraction values are dependent upon the frequency of light. For visible light, the n value does not show a large variation with frequency, but nonetheless it shows a variation. For instance for some types of glass, the n value for frequencies of violet light is 1.53; and the n value for frequencies of red light is 1.51. The absorption and re-emission process causes the higher frequency (lower wavelength) violet light to travel slower through crown glass than the lower frequency (higher wavelength) red light. It is this difference in n value for the varying frequencies (and wavelengths) that causes the dispersion of light by a triangular prism. Violet light, being slowed down to a greater extent by the absorption and re-emission process, refracts more than red light. Upon entry of white light at the first boundary of a triangular prism, there will be a slight separation of the white light into the component colors of the spectrum. Upon exiting the triangular prism at the second boundary, the separation becomes even greater and ROYGBIV is observed in its splendor.

The answer?

 

 

DISPERSION.  I say dispersion. 

I  assume you mean how light behaves IN a prism - the physical laws are refraction and dispersion.

Im not sure, but ill guess Dispersion.


Deviation angle and dispersion

Ray angle deviation and dispersion through a prism can be determined by tracing a sample ray through the element and using Snell's law at each interface. For the prism shown at right, the indicated angles are given by

{\displaystyle {\begin{aligned}\theta '_{0}&=\,{\text{arcsin}}{\Big (}{\frac {n_{0}}{n_{1}}}\,\sin \theta _{0}{\Big )}\\\theta _{1}&=\alpha -\theta '_{0}\\\theta '_{1}&=\,{\text{arcsin}}{\Big (}{\frac {n_{1}}{n_{2}}}\,\sin \theta _{1}{\Big )}\\\theta _{2}&=\theta '_{1}-\alpha \end{aligned}}}.

All angles are positive in the direction shown in the image. For a prism in air {\displaystyle n_{0}=n_{2}\simeq 1}. Defining {\displaystyle n=n_{1}}, the deviation angle {\displaystyle \delta } is given by

{\displaystyle \delta =\theta _{0}+\theta _{2}=\theta _{0}+{\text{arcsin}}{\Big (}n\,\sin {\Big [}\alpha -{\text{arcsin}}{\Big (}{\frac {1}{n}}\,\sin \theta _{0}{\Big )}{\Big ]}{\Big )}-\alpha }

If the angle of incidence {\displaystyle \theta _{0}} and prism apex angle {\displaystyle \alpha } are both small, {\displaystyle \sin \theta \approx \theta } and {\displaystyle {\text{arcsin}}x\approx x} if the angles are expressed in radians. This allows the nonlinear equation in the deviation angle {\displaystyle \delta } to be approximated by

{\displaystyle \delta \approx \theta _{0}-\alpha +{\Big (}n\,{\Big [}{\Big (}\alpha -{\frac {1}{n}}\,\theta _{0}{\Big )}{\Big ]}{\Big )}=\theta _{0}-\alpha +n\alpha -\theta _{0}=(n-1)\alpha \ .}

The deviation angle depends on wavelength through n, so for a thin prism the deviation angle varies with wavelength according to

{\displaystyle \delta (\lambda )\approx [n(\lambda )-1]\alpha }.

not sure, dont know much about it

A prism is something that splits light.  Maybe you should read that chapter again.  

Refraction. Prisms refract light when they split that light into the various colors, (Roy G Biv).

And speaking of prisms I've got a neat example sitting here on my desk. It very accurately splits incoming light into three perfect images (or it did before it developed a hairline crack while in service in a broadcast TV camera): one with all the red light, one with all the blue light and one with all the green light.