1.

An optical fibre consists of core of m­1 surrounded by a cladding of m2 < m1. A beam of light enters from air at an angle a with axis of fibre. The highest a for which ray can be travelled through fibre is

A. \[{{\cos }^{-1}}\sqrt{\mu _{2}^{2}-\mu _{1}^{2}}\]
B. \[{{\sin }^{-1}}\sqrt{\mu _{1}^{2}-\mu _{2}^{2}}\]
C. 30 V
D. \[{{\sec }^{-1}}\sqrt{\mu _{1}^{2}-\mu _{2}^{2}}\]
Answer» C. 30 V


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