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Geometrical Optics question

2022 · 30 Jun · Shift 1 · Q65
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Geometrical Optics question

2022 · 30 Jun · Shift 1 · Q65

JEE MainPhysicsGeometrical OpticsNumerical+4 / −1
The refractive index of an equilateral prism is 2\sqrt 22​. The angle of emergence under minimum deviation position of prism, in degree, is ‾\underline{\hspace{2cm}}​.
Numerical answer
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Correct answer: 45

  1. Given data

    • Prism is equilateral, so prism angle: A=60∘A = 60^\circA=60∘
    • Refractive index: μ=2\mu = \sqrt{2}μ=2​
  2. Condition for minimum deviation For a prism at minimum deviation, i=ei=ei=e and r1=r2=A2r_1=r_2=\frac{A}{2}r1​=r2​=2A​

    Hence, r=60∘2=30∘r = \frac{60^\circ}{2} = 30^\circr=260∘​=30∘

  3. Apply Snell's law at first face At air-to-prism interface, μ=sin⁡isin⁡r\mu = \frac{\sin i}{\sin r}μ=sinrsini​

    So, 2=sin⁡isin⁡30∘\sqrt{2} = \frac{\sin i}{\sin 30^\circ}2​=sin30∘sini​

    Since, sin⁡30∘=12\sin 30^\circ = \frac{1}{2}sin30∘=21​

    Therefore, sin⁡i=2⋅12=22\sin i = \sqrt{2}\cdot \frac{1}{2} = \frac{\sqrt{2}}{2}sini=2​⋅21​=22​​

    Thus, i=45∘i = 45^\circi=45∘

  4. Find angle of emergence Under minimum deviation, e=ie=ie=i

    Therefore, e=45∘e = 45^\circe=45∘

  5. Final answer The angle of emergence is: 45\boxed{45}45​

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