NEETPhysicsGeometrical OpticsMCQ+4 / −1
The angle of a prism is A. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence 2 A on the first surface returns back through the same path after suffering reflection at the silvered surface.
The refractive index , of the prism is
The refractive index , of the prism is
- A2sinA
- B2cosA
- CcosA
- DtanA
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Correct answer: B

Applying Snell’s law at surface PQ,
1sini = $\mu $sinr
$\mu $ = $${{\sin i} \over {\sin r}}$$ = $${{\sin 2A} \over {{\mathop{\rm sinA}\nolimits} }}$$ = 2cosA
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