Rankers Physics

Refraction by Prism: Practice Problem & Solution

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: (2017-Delhi)
$6^\circ$
$8^\circ$
$10^\circ$
$4^\circ$

Solution Explained:

To solve this problem, we apply the core principles of Refraction by Prism. Understanding the underlying formula is key to arriving at the correct answer below:

For dispersion without deviation, the net deviation produced by the combination must be zero.
$(\mu_1 - 1)A_1 = (\mu_2 - 1)A_2$, where A and $\mu$ are refracting angle and refractive index.
$(1.42 - 1) \times 10^\circ = (1.7 - 1) \times A_2$, giving $4.2 = 0.7 A_2$, so $A_2 = 6^\circ$.

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