If One Face Of A Prism Of Prism Angle 30o and  is Silvered, The Incident Ray Retraces Its Initial Path. The Angle Of Incidence Is:

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If one face of a prism of prism angle 30o and  is silvered, the incident ray retraces its initial path. The angle of incidence is:


Correct option is



It is clear from the figure that the ray will retrace the path when the refracted ray QR is incident normally on the polished surface AC. Thus angle of refraction r = 30o.

We know that μ = sin i/sin r







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Angle of a prism is A and its one surface is silvered. Light rays falling at an angle of incidence of 2A on first surface return back through the same path after suffering reflection at the second silvered surface. Refractive index of the material is: