Features Of Dispersion Of Light Through Prism

A prism is a homogeneous, transparent medium bounded by two plane surfaces inclined at an angle A with each other. These surfaces are called the refracting surfaces, and the angle between them is called the angle of prism.

Dispersion

The dispersion of white light occurs when light passes through a prism. The splitting of white light into various colours is called dispersion. In 1666 AD, Sir Isaac Newton recorded this incident. He found that white light consists of seven unique colours as it travels through a glass prism.

Dispersion of Light Through a Prism

White light consists of several wavelengths (colours) of light: violet, indigo, blue, green, yellow, and red. Red has the longest wavelength and violet has the shortest. Red light is the least deviated, while violet light is the most deviated. Light scattering is determined by the wavelength of the light. Each colour corresponds to a certain wave frequency, and different frequencies of light waves move in different ways while passing through a prism. When white light moves from one optical medium to another, various colours of the light divide because all wavelengths have different angles of deviation. This process of light splitting into its components as a result of refraction is called dispersion.

Spectrum

It is possible to construct a band of seven colours using white light by using a narrow beam of light and a glass prism. This band is known as the spectrum. White light is made up of seven colours. You may not see all seven colours as it is caused by colour overlapping.

The wavelengths of different colours in the light spectrum are different. The degree of bending of the light path is determined by the angle formed by the incident beam of light with the surface, as well as the ratio of the refractive indices of the two media. As a result, when white light is emitted by a prism, it scatters throughout its colour spectrum.

Optical Density

The optical densities of different materials are different. The optical density is a measurement of a material’s ability to delay/block light as it passes through it. For example: Take two mediums; glass and air. When a light beam of light is passed from air to glass, the speed of light is reduced. Hence, we can conclude that the glass is denser than the air. On the other hand, if the same light is passed from glass to air, the speed is increased. As a result, whereas a light wave travels at c (3.00 x 108 m/s) through a vacuum, it travels at speeds less than c through a transparent medium.

The notion of optical density explains why the speed of light reduces as it passes through a  particular medium, as well as the significance of the wavelength of light.

Index of Refraction

The index of refraction value is a numerical representation of a medium’s optical density. It can be defined as the ratio of the speed of light in a vacuum to the speed of light in the material medium. A higher index of refraction means that a particular medium can retain absorbed light energy for longer periods.

Higher frequency (lower wavelength) violet light travels slower through glass than lower frequency (higher wavelength) red light due to the absorption and re-emission process. The dispersion of light by a triangular prism is caused by the variation in n values for changing frequencies (and wavelengths). Violet light refracts more than red light because it is slowed down more by the absorption and re-emission process.

Angle of Deviation

The angle of deviation is just a phrase used to describe the degree of overall refraction induced by a light beam passing through a prism. The angle of deviation is the angle formed by the incident beam of light entering the prism’s first side and the refracted ray emerging from the prism’s accompanying side. The deviation is inversely proportional to the wavelength. An observer may see the component colours of visible light separated from one another because different colours of light emerge from a triangular prism at different angles.

Causes of Dispersion of Light

The reason for light dispersion via the prism is that white light has a spectrum of seven colours, each with its angle of deviation. Refraction is the sole reason for light dispersion. Snell’s law states if the polychromatic light (light containing lights of different wavelengths) enters from a less dense medium to a more dense medium, then each colour of light follows a separate path.

Snell’s law states the relationship between the angles of incidence and refraction as light passes from one medium to another. Dispersion and refraction do not occur in the case of normal incidence.

Conclusion

 White light is made up of seven different colours, namely Violet, Indigo, Blue, Green, Yellow, Orange, and Red. When white light passes through the prism, it is divided into its component colours. This process of splitting white light constituent colours is known as Dispersion. The band of colours thus forms a pattern called a spectrum. When white light moves from one optical medium to another, various colours of the light divide because all wavelengths have different angles of deviation. We can say that the sole reason for dispersion is refraction, which is the bending of light as it travels through a transparent medium known as refraction.