Refraction and Dispersion of Light Through A Prism

The prism is glass or any transparent material in the prism form that is triangular with the refracting surfaces at the acute angle, with one another and causes the separation of light into a spectrum of colors.

Refraction Through Prism

The light rays suffer two refractions when they are passing through the prism, and they undergo some deviation through a certain angle at its original path. The angle that is subtended between the direction of an incident ray of light and an emergent ray of light from the prism is the angle of deviation.

By the calculation of the refractive index of the material of prism, the following prism formula can be stated.

The refraction is bending of light in the path when it is traveling from one medium to another medium. The degree of refraction is dependent on the wavelength of light. The deviation for each light is different due to the different wavelengths. In the path of light, there is an inverse relationship between wavelength and deviation. The prism is only acting as a medium for the dispersion of light that is made up of 7 different colors. The phenomenon of refraction can be observed by the falling of light on the prism. Due to the velocity difference of the prism, the frequency and wavelength of the deviated colors are also different, so they are deviating differently from different angles.

Dispersion of Light

The splitting of white light, into the constituent colors, in a sequence of VIBGYOR, when it is passing through the prism is known as the dispersion of light. Due to this dispersion, the angle subtended between the direction of red and violet emergent light rays from the prism is known as angular dispersion. The angular dispersion can be produced by the prism for the white light and it is the difference in the angle of deviation of the two extreme colors, such as red and violet.

When there are sunshine and rain simultaneously, then it causes the formation of a rainbow. Each of the raindrops is having a different shape, and consistency as compared to glass prism but in both cases, light is affected in a similar fashion. When the white light from the sun is traveling from air to water drop then the constituent colors are slowing down at the various frequencies and speed. When the violet light is entering the raindrop, it is bending at the relatively sharper angle. Some of the light is passing back to the air and it is again reflected.


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