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Geometrical Optics question

2024 · 6 Apr · Shift 1 · Q87
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  5. /2024 · 6 Apr · Shift 1 · Q87

Geometrical Optics question

2024 · 6 Apr · Shift 1 · Q87

JEE MainPhysicsGeometrical OpticsNumerical+4 / −1
The refractive index of prism is μ=3\mu=\sqrt{3}μ=3​ and the ratio of the angle of minimum deviation to the angle of prism is one. The value of angle of prism is ‾\underline{\hspace{2cm}}​∘^\circ∘.
Numerical answer
View written solutionFree

Correct answer: 60

  1. Given data

    • Refractive index of prism: μ=3\mu = \sqrt{3}μ=3​
    • Ratio of angle of minimum deviation to angle of prism is one: δmA=1  ⟹  δm=A\frac{\delta_m}{A}=1 \implies \delta_m=AAδm​​=1⟹δm​=A
  2. Formula for refractive index at minimum deviation

    For a prism in air, μ=sin⁡(A+δm2)sin⁡(A2)\mu = \frac{\sin\left(\frac{A+\delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)}μ=sin(2A​)sin(2A+δm​​)​

  3. Use the condition δm=A\delta_m = Aδm​=A

    Substitute into the formula:

    = \frac{\sin A}{\sin\left(\frac{A}{2}\right)}$$ Since $\sin A = 2\sin\left(\frac{A}{2}\right)\cos\left(\frac{A}{2}\right)$, $$\mu = \frac{2\sin\left(\frac{A}{2}\right)\cos\left(\frac{A}{2}\right)}{\sin\left(\frac{A}{2}\right)} = 2\cos\left(\frac{A}{2}\right)$$
  4. Substitute μ=3\mu = \sqrt{3}μ=3​

    3=2cos⁡(A2)\sqrt{3} = 2\cos\left(\frac{A}{2}\right)3​=2cos(2A​) cos⁡(A2)=32\cos\left(\frac{A}{2}\right) = \frac{\sqrt{3}}{2}cos(2A​)=23​​

  5. Find AAA

    A2=30∘\frac{A}{2} = 30^\circ2A​=30∘ A=60∘A = 60^\circA=60∘

  6. Final answer

    The angle of prism is: 60∘\boxed{60^\circ}60∘​

  7. Comparison with stored correct answer

    Stored correct answer = 606060

    Our derived answer matches the stored answer.

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