Question

What is the cause of the dispersion of white light through a glass prism? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prisms.

Answer 1

The dispersion of white light occurs because of the varying speeds of different colored lights through different media. White light consists of seven colors. The speeds of these colored lights are the same through the air. However, their speeds vary in other media. Therefore, when white light enters from air to a glass prism then its component colors get refracted by different angles. As a result, dispersion occurs.

A ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prisms is given below:

When white light of the Sun passes through the first prism, it gets dispersed into its seven component colors. When all the seven colors of the spectrum pass through the second prism then a beam of white light emerges from the other side of the second prism.