Question

Prism angle of a prism is ${10}^{\circ }$. Refractive index for red and violet colour is 1.51 and 1.52 respectively. Then the dispersive power of the prism is

• A. 0.019
• B. 0.011
• C. 1.515
• D. 0.029

Answer 1

The correct option is A 0.019

Dispersive power $\omega =\frac{\theta }{{\delta }_Y}$
where $\theta$ is the angle of dispersion and ${\delta }_Y$ is the angle of mean deviation (yellow light)
$\theta =({\mu }_V-{\mu }_R)A$ and ${\delta }_Y=({\mu }_Y-1)A$ where ${\mu }_Y\approx \frac{{\mu }_V+{\mu }_R}{2}=1.515$
$\therefore \omega =\frac{1.52-1.51}{1.515-1}=\frac{0.01}{0.515}=0.019$