Phenomena of Deviation of Light by a Prism

The deviation of light occurs when a beam of light changes route as it travels from one medium to another. Refraction occurs twice when a ray of light passes through a prism. It enters and exits the prism twice. Light rays bend towards the normal while passing from an optically rarer media to an optically denser one. Light rays bend away from the typical direction when they move from an optically denser to an optically rarer material. The angle of deviation is defined as the angle formed by the incident and emerging rays.

Prism

A transparent optical device with flat, polished surfaces designed to refract light is known as an optical prism. Objects having two parallel surfaces are not prisms, as they must have at least one angled surface. Prisms can be created out of any material that is transparent to the wavelengths they are intended for. Glass, acrylic and fluorite are common materials.

Types of Prisms

• Dispersive Prism 

Because the refractive index of light varies with frequency, dispersive prisms are used to separate light into its constituent spectral colours. White light entering the prism is a combination of frequencies, each of which bends somewhat differently. Because blue light is slower than red light, it bends more.

• Reflective Prism

To flip, invert, spin, divert or displace the light beam, reflective prisms are employed to reflect it. Without the prisms, the image would be upside down for the user in binoculars or single-lens reflex cameras.

• Beam-splitting Prism

A beam-splitter cube may be made by depositing various thin-film optical layers on the hypotenuse of one right-angled prism and cementing it to another prism. The thin layer determines the overall optical performance of a cube.

• Polarising Prism

Polarising prisms, which divide a beam of light into components of changing polarisation by birefringence, belong to a different class. They have very low losses in the visible and UV areas and their extinction ratio is often greater than that of other types of polarizers. Total internal reflection may or may not be used.

Deviation in Prism

The deviation of light occurs when a beam of light changes route as it travels from one medium to another. Refraction occurs twice when a beam of light travels through a prism. It enters and exits the prism twice. Light rays bend towards the normal while passing from an optically rarer media to an optically denser one. Light rays bend away from the normal when they move from an optically denser to an optically rarer material. The angle of deviation is the difference in direction between the incident and emerging rays.

Factors on which the angle of deviation is dependent:

• The refracting angle of the prism
• The material of the prism
• The angle of incidence

Minimum Deviation

The refracted light in a prism is parallel to its base when it has the smallest deviation. The light beam is symmetrical around the prism’s symmetry axis, in other words. In addition, the refraction angles are all the same. In addition, the incidence and emergence angles are identical.

By making use of the prism’s geometry, the formula for the lowest deviation may be found. Using the foregoing qualities, the variables in Snell’s law may be replaced in terms of Deviation and Prism Angles.

Maximum Deviation

As the angle of incidence increases, the deviation decreases until the angle of the lowest deviation is attained. As the angle of incidence rises, the deviation angle increases again.

Maximum deviation can occur under two conditions:

1) When the angle of incidence is 90 degrees, the maximum deviation occurs. Because the incoming light beam “grazes” down the prism surface, this is known as grazing incidence.

2) The emerging light beam grazes along the prism surface after leaving the prism, which is another criterion for maximum deviation. This is much the same as the previous condition, except with the light rays pointing in the other direction.

Conclusion

The deviation of light occurs when a beam of light varies its course as it travels from one medium to another. When the light goes through a prism, it refracts twice. It enters the prism once and exits it twice. The angle of deviation is the angle formed by the direction of the incident ray and the direction of the emerging ray. When the incident ray enters the prism, it bends towards the normal and when it exits the prism, it bends away from the normal. The angle of deviation reduces as the angle of incidence rises. It rises with an increase in the angle of incidence after reaching the lowest value.