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JEE Main 2020 (2 Sep, Shift 2) · Total Internal Reflection

Total Internal Reflection question from JEE Main 2020 (2 Sep, Shift 2)

Q40JEE Main 2020 · 2 SEP · SHIFT 2Difficult

Total Internal Reflection

A light ray enters a solid glass sphere of refractive index μ=3\mu = \sqrt{3} at an angle of incidence 60°. The ray is both reflected and refracted at the farther surface of the sphere. The angle (in degrees) between the reflected and refracted rays at this surface is ________.

Numerical answer type. Work it out, then open the answer.

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Answer: 90

  1. At entry: sin⁡r=sin⁡60∘3=12⇒r=30∘\sin r = \frac{\sin 60^\circ}{\sqrt{3}} = \frac{1}{2} \Rightarrow r = 30^\circ.
  2. Inside a sphere the chord makes equal angles with both radii, so incidence at the far surface is 30∘30^\circ.
  3. Reflected ray makes 30∘30^\circ with the normal; refracted ray emerges at 60∘60^\circ with the normal on the other side.
  4. Angle between them =180∘−30∘−60∘=90∘= 180^\circ - 30^\circ - 60^\circ = 90^\circ
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