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NEET 2018
Exam
NEET
Year
2018
Subject
Physics
Chapter
Ray Optics

NEET 2018 · Physics · Ray Optics

The refractive index of the materiel of a prism is 2 and the angle...

The refractive index of the materiel of a prism is 2\sqrt{2} and the angle of the prism is 30o.{30}^{o} . One of the two refracting surface of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism isThe refractive index of the materiel of a prism is 2 and the angle of the prism is 30 ^ o . One of the two refracting

Options

  1. A30o{30}^{o}
  2. B45o{45}^{o}
  3. C60o{60}^{o}
  4. DZero

Correct answer

B. 45o{45}^{o}

Step-by-step solution

by principle of reversibility, the beam will return its path when it strikes the mirror perpendicularly
The refractive index of the materiel of a prism is 2 and the angle of the prism is 30 ^ o . One of the two refracting

r2=0,r1=A=30o{r}_{2} = 0, {r}_{1} = A = {30}^{o}
∴r1+r2=A∴ {r}_{1} + {r}_{2} = A in a prism
Applying Snell's law at P sini=2sin30o=2×12=12sin i = \sqrt{2}sin {30}^{o} = \sqrt{2} \times \dfrac{1}{2} = \dfrac{1}{\sqrt{2}}

∠i=45o∠i = {45}^{o}

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