A thin prism having refracting angle $10^{\circ}$ is made of glass of refractive index 1.42. This pr

Question

A thin prism having refracting angle $10^{\circ}$ is made of glass of refractive index 1.42. This prism is combined with another thin prism of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be\

Professor PC Thomas Classes · Answer

(a) : The condition for dispersion without deviation is given as $(\mu-1) A=\left(\mu^{\prime}-1ight) A^{\prime}$\ Given $\mu=1.42, A=10^{\circ}, \mu^{\prime}=1.7, A^{\prime}=$ ?\ $	herefore \quad(1.42-1) 	imes 10=(1.7-1) A^{\prime}$ $$ (0.42) 	imes 10=0.7 	imes A^{\prime} $$ or $\quad A^{\prime}=\frac{0.42 	imes 10}{0.7}=6^{\circ}$\