Dispersion, Diffraction & Polarization

Dispersion of light

It is the phenomenon of splitting of a beam of white light into its constituent colors on passing through a prism. The band of seven colors so obtain is called the spectrum. Cause of dispersion is each color has its own characteristics Wavelength (λ).

The order of colors from lower end of the spectrum is Violet(V), Indigo(I), Blue (B), Green(G), Yellow (Y), Orange (O), & Red (R); & can be recollected by the word VIRGYOR. In the above figure violet color is deviates from maximum angle & Red color deviates from minimum angle. Dispersion is denoted by ઠ(Delta).

ઠ = (μ−1)A

where μ= Refractive Index of Prism’s medium

           A= Angle of Prism.

Angle of Dispersion: Angle of Dispersion = ઠ_V - ઠ_R

                                    Angle of Dispersion = (μ_V – 1)A – (μ_R – 1)A

                                    Angle of Dispersion = (μ_V – μ_R)A

Dispersive Power: It is defined as the ratio of angular dispersion to the mean deviation produced by the prism. It is denoted by ω.

Note: It is use to find out the dispersive capacity of a medium.

Diffraction of light

It is the phenomenon of bending of light around corners of an obstacle or aperture in the path of light.

This deviation becomes much more pronounced when the dimension of the aperture is less.

out of the three cases shown, diffraction is most pronounced when slit width is smallest i.e.; a = 1.5 cm.

Polarization of light 

A light wave that is vibrating in more than one plane is referred as unpolarized light. Polarized light waves are light wave in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization.

E.g.when we observe the headlight of vehicles; it has horizontal lines. These horizontal lines are opening of the polarizer. It is made up of the crystal not glass. When the headlight passes through these opening it becomes a light which vibrates in a single plane(i.e. horizontal plane) only so that it does not effect the eyes of the people who is coming towards you & we are also able to see the road clearly.