Q 12-09-074JEE MainJEE Main 2025 (28 Jan, Shift 1)Easy
A thin prism $P_1$ with angle $4^\circ$ made of glass having refractive index $1.54$ is combined with another thin prism $P_2$ made of glass having refractive index $1.72$ to get dispersion without deviation. The angle of the prism $P_2$ in degrees is
Answer: (A) $3$
A thin prism deviates light by $\delta = (\mu - 1)A$. For zero net deviation the two deviations must cancel:
$$(\mu_1 - 1)A_1 = (\mu_2 - 1)A_2$$
$$0.54\times4 = 0.72\times A_2 \Rightarrow A_2 = \frac{2.16}{0.72} = 3^\circ$$
Solution by Sreeraj P, M.Sc Physics