Question

Diagrams given below shows two equilateral glass prisms and a ray of white light incident on prism A.

1. Copy the diagram and trace the course of white ray of light, till it strikes the screen.
2. Write about two conclusions which you can draw about the nature of white light.

Answer 1

(a)

Prism A splits the white light into seven colours (dispersion). Prism B is placed upside down, so it bends each colour back by the same amount. The colours join up again and come out as one beam of white light. This beam is parallel to the original ray and makes a white patch on the screen.

(b) Two conclusions about white light:

1. White light is made up of seven colours (VIBGYOR).
2. These seven colours can be combined again to give white light.