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JEE Main · 2021 · 25 Jul 2021 · Shift 1 · Geometrical Optics

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A ray of laser of a wavelength 630 nm is incident at an angle of at the diamond-air interface. It is going from diamond to air. The refractive index diamond is 2.42 and that of air is 1. Choose the correct option.
  1. (A)angle of refraction is
  2. (B)angle of refraction is
  3. (C)angle of refraction is
  4. (D)refraction is not possible✓ Correct

Answer: (D)

Solution

The ray goes from the denser medium into air, so a critical angle exists and is given by , that is . The angle of incidence is larger than this. Snell's law would demand

and no angle has a sine greater than one. The whole beam is turned back into the diamond by total internal reflection, so refraction is not possible.

JEE Main · 2021 · 25 Jul 2021 · Shift 1 · Single correct option

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