Question

If a glass prism is dipped in water, its dispersive power

• A. increases
• B. decreases
• C. does not change
• D. may increase or decreases depending on whether the angle of the prism is less than or greater than ${60}^{\circ }$

Answer 1

Answer: (B)

decreases

Glass prism works on the principle that lights with different colours travels with different speed in solid and liquid medium. So when a glass prism is dipped in water the light that reaches it is already some what dispersed by water, and the prism does still more. Hence its dispersive power decreases.