Question

If velocity of light in air and water is 3 x 10⁸ ms^-1 and 2 x 10⁸ ms^-1 respectively, then what should be its critical angle ?

(A) \(\sin^{-1}(\frac 32)\)

(B) \(\tan^{-1}(\frac 32)\)

(C) \(\tan^{-1}(\frac 23)\)

(D) \(\sin^{-1}(\frac 23)\)

Answer 1

Correct option is (D) \(\sin^{-1}(\frac 23)\)

\(\mu = \frac{3 \times 10^8 ms^{-1}}{2\times 10^8ms^{-1}} = \frac 32\)

\(C = \sin^{-1}(\frac 1\mu)\)

\(= \sin^{-1}\left(\frac 1{\frac 32}\right)\)

\(=\sin^{-1}(\frac 23)\)