Question

White light is incident on one of the refracting surfaces of a prism of angle $5^\circ$. If the refractive indices for red and blue colours are $1.641$ and $1.659$ respectively, the angular separation between these two colours when they emerge out of the prism is

• A. $0.9^\circ$
• B. $0.09^\circ$
• C. $1.8 ^\circ$
• D. $1.2 ^\circ$

Answer 1

Answer: (B)

$0.09^\circ$

Answer 2

Angular dispersion,
$\delta_{b}-\delta_{r} =\left(\mu_{b}-\mu_{r}\right) A$
$=(1.659-1.641) 5^{\circ}$
$=0.09^{\circ}$