Question

The refractive angles of two crown glass prisms are ${10}^{\circ }$ and ${20}^{\circ }$ respectively. What is the ratio of the dispersive powers?

• A. $1:2$
• B. $2:1$
• C. $1:1$
• D. $1:4$

Answer 1

The correct option is A $1:2$

The dispersive power of the prism is directly proportional to refractive angle,

$P\propto \theta$

$\frac{P_1}{P_2}=\frac{{\theta }_1}{{\theta }_2}=\frac{{10}^0}{{20}^0}$

Ratio, $P_1:P_2=1:2$

The correct option is A.