Question

If the white ray falls on the system arranged in the given way, then what will be the colour of the output light coming from the third prism?

• A. Only yellow colour
• B. 7 different colours
• C. Only red colour
• D. Only violet colour

Answer 1

The correct option is B 7 different colours

Light disperses into 7 colours after passing through the first prism. The seven colours coming out from the 1st prism fall on the 2nd prism and recombine again because of the reversal of dispersion phenomenon. The emergent light from the 2nd prism is therefore a white light beam which falls on third prism. Since the incident light is a white light ray, the emergent light from the third prism is a 7-coloured VIBGYOR spectrum.