Glass Prism - Dispersion Of White Light

Have you seen a prism? Yes that small block of glass that splits light into different colors. How does that happen, the white light splits into different colors when passed through a prism? Let’s try to find some answers to these queries. The answer lies in the fact that the speed of light and its components vary inversely with the refraction index of the medium. When light waves travel from one medium to another, they get refracted as a result of difference in optical density of both the mediums. Refraction is

Refraction is deviation in the path of the light when it travels from one optical medium to the other. The degree of refraction depends on the wavelength of the light, different wavelengths experience different degrees of deviation. White light is primarily composed of light of different wavelengths (colors) viz. violet, indigo, blue, green, yellow and red with red having the highest wavelength while the violet having the lowest wavelength.

The deviation in the path of the light is inversely proportional to the wavelength. Red light suffers the least amount of deviation and violet the most. Since all the wavelengths suffer different angles of deviation, when white light passes from one optical medium to another, different colors of light split and this phenomenon of splitting of light into its components as a result refraction is called dispersion.

Prism - Dispersion Of White Light

Dispersion of white light by a glass prism

When white light is made to pass through a prism, a spectrum of seven colors is formed which shows that white light is a mixture of seven different colors. Prism only acts as a medium for the separation of the seven colors. When light falls on the glass prism, refraction takes place. Since the wavelength of different components of light is different and the frequency is constant, each component gets deviated by a different angle due to the difference in velocity in the glass medium. The red color having the maximum wavelength deviates the least and forms the upper part of the spectrum whereas violet having the least wavelength deviates the most.

Learn more about different phenomena associated with light waves and their behavior under different conditions with the team of expert mentors at Byju’s.

Practise This Question

Velocity of light in glass is 2×108 ms1 and in air is 3×108 ms1.  If the ray passes through glass to air, calculate the value of critical angle.