Question

In an achromatic combination of two prisms, the ratio of the deviations produced by the two prisms is $2:3$, the ratio of their dispersive power is :

• A. $2:3$
• B. $3:2$
• C. $1:1$
• D. $4:9$

Answer 1

The correct option is B $3:2$

In an achromatic combination of two prisms,

The ratio of the deviations produced by the two prisms is inversely proportional to the ratio their dispersive power.

$\therefore \frac{{\delta }_1}{{\delta }_2}=\frac{2}{3}=\frac{P_2}{P_1}$

$\therefore \frac{P_1}{P_2}=\frac{3}{2}$