A narrow beam of white light is shown to pass through a triangular glass prism

Human Eye & Colourful World (C10)

In the figure given below, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism, it produces a spectrum XY on the screen.

  1. Name the phenomenon.
  2. State the colours seen at X and Y.
  3. Why do different colours of white light bend at different angles through a prism?

Answer

(i) The phenomenon is called dispersion.

(ii) X - Violet,  Y - Red

(iii) Different colours of white light bend through different angles with respect to the incident beam of light due to difference in speed of light of different wavelengths.