# Dispersion

By the word dispersion we usually denote a separation of light to its frequency components. The wave theory explains this separation by a frequency dependence of the material’s refractive index n, which is expressed as a ratio of the speed of light in vacuum *c _{0}* relative to that

*c*in the substance:

*n = c*.

_{0}/cIn our computer program we simulate the dispersion phenomenon on the bases of the sum-over-paths method, where photon is the basic particle of the light, which moves at the speed *c _{0}* of light in vacuum. Therefore, the light speed decrease in materials is the result of a zigzag movement of the photons. In the section Point-to-Point paths, the refractive index is expressed as a ratio of the mean length

*L*of the zigzag path between two points relative to the straight-line distance

*L*of the considered points:

_{0}*n = L/L*. This equation is used in the program for computing the length

_{0}*L*in a matter (glass) with given refractive index

*n*and the straight-line distance

*L*of initial points on an air-glass boundary and the terminal points on screen.

_{0}

*Fig. 15. Dispersion *(dispersion.exe)

The *Fig. 15* illustrates the dispersion. A mixture of three monochromatic lights (red, green and blue) is accident on the air-glass interface at a not-perpendicular angle. Separation of the R, G, B components is depicted by their interference patterns in corresponding colours. Spectrum illustrates the light, as it would be seen on a screen. On the right-hand side of the *Fig. 15* there are shown some Cornu spirals, which have formed the green interference pattern at the relevant points. Interference patterns in *Fig.15* confirm the frequency dependence of the refraction effect. Blue light is refracted more than the green and the red ones