Question

A thin prism $P_1$ with angle $4^\circ$ and made from glass of refractive index 1.54 is combined with another thin prism $P_2$ made from glass of refractive index 1.72 to produce dispersion without deviation. The angle of the prism $P_2$ is

• A. $5.33^\circ$
• B. $4^\circ$
• C. $3^\circ$
• D. $2.6^\circ$

Answer 1

Answer: (C)

Deviation $\delta =(\mu-1)A$
Given $\delta_{net}=0$
$\therefore \, \, \, \, \, \, \, (\mu_1-1)A_1=(\mu_2-1)A_2$
$or \, \, \, \, \, \, \, \, \, \, \, \, \, \, A_2=\frac{(\mu-1)}{(\mu_2-1)}A_1$
$ =\frac{(1.54-1)}{(1.72-1)}(4^\circ)=3^\circ$
$\therefore $ Correct option is (c).