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Question: Answered & Verified by Expert
A thin glass prism of angle $9^{\circ}$ with refractive index 1.4 is combined with another glass prism of refractive index 1.6 as shown in the figure. The combination of the prism provides dispersion without deviation. Determine the angle $(A)$ of the second prism.

PhysicsRay OpticsTS EAMCETTS EAMCET 2020 (11 Sep Shift 2)
Options:
  • A $9^{\circ}$
  • B $12^{\circ}$
  • C $6^{\circ}$
  • D $4^{\circ}$
Solution:
2887 Upvotes Verified Answer
The correct answer is: $6^{\circ}$
For dispersion without deviation through a prism combination,
$\delta_{m_1}=\delta_{m_2} \Rightarrow A_1\left(\mu_1-1\right)=A_2\left(\mu_2-1\right)$
Here, $A_1=9^{\circ}, \mu_1=1.4$ and $\mu_2=1.6$
$\therefore \quad A=A_2=9 \times \frac{(1.4-1)}{(1.6-1)}=9 \times \frac{0.4}{0.6}=6^{\circ}$

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