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Physics · Geometrical Optics

JEE Main 2026 — 23 January, Morning Shift — Question 26

A thin prism with angle 5∘5^{\circ} of refractive index 1.72 is combined with another prism of refractive index 1.9 to produce dispersion without deviation. The angle of second prism is ____\_\_\_\_ .

  1. Option A:

    4.5∘4.5^{\circ}

  2. Option B:

    6∘6^{\circ}

  3. Option C:

    4∘4^{\circ}

    Correct
  4. Option D:

    5∘5^{\circ}

Answer: C

Step-by-step solution

δnet =0\delta_{\text {net }}=0

δ1+δ2=0(μ1−1)A1+(μ2−1)A2=0 A2=(μ1−1)A1(μ2−1)A2=(1.72−1)(1.9−1)×5∘=4∘\begin{aligned} & \delta_{1}+\delta_{2}=0 & \left(\mu_{1}-1\right) \mathrm{A}_{1}+\left(\mu_{2}-1\right) \mathrm{A}_{2}=0 & \mathrm{~A}_{2}=\frac{\left(\mu_{1}-1\right) \mathrm{A}_{1}}{\left(\mu_{2}-1\right)} & \mathrm{A}_{2}=\frac{(1.72-1)}{(1.9-1)} \times 5^{\circ}=4^{\circ} \end{aligned}

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Paper
23 January, Morning Shift
Subject
Physics
Chapter
Geometrical Optics
Topic
Apparent Depth, Glass Slab, Prism and Dispersion

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