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NEET 1992 (AIPMT) · Prism, Dispersion & Scattering

Prism, Dispersion & Scattering question from NEET 1992 (AIPMT)

Q95NEET 1992 · AIPMTMedium

Prism, Dispersion & Scattering

There is a prism with refractive index equal to 2\sqrt{2} and the refractive angle equal to 30∘30^\circ. One of the refractive surface of the prism is polished. A beam of monochromatic light will retrace its path if its angle of incidence over the refracting surface of the prism is

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Answer: (c)

  1. Retracing needs normal incidence on the polished face, so r=A=30∘r = A = 30^\circ.
  2. sin⁡i=2sin⁡30∘=12\sin i = \sqrt{2}\sin 30^\circ = \frac{1}{\sqrt{2}}
  3. So the answer is (c) 45∘45^\circ.
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