JEE MAIN - Physics (2022 - 29th June Evening Shift - No. 4)
The speed of light in media 'A' and 'B' are $$2.0 \times {10^{10}}$$ cm/s and $$1.5 \times {10^{10}}$$ cm/s respectively. A ray of light enters from the medium B to A at an incident angle '$$\theta$$'. If the ray suffers total internal reflection, then
$$\theta = {\sin ^{ - 1}}\left( {{3 \over 4}} \right)$$
$$\theta > {\sin ^{ - 1}}\left( {{2 \over 3}} \right)$$
$$\theta < {\sin ^{ - 1}}\left( {{3 \over 4}} \right)$$
$$\theta > {\sin ^{ - 1}}\left( {{3 \over 4}} \right)$$
Explanation
$${\mu _A} = {{3 \times {{10}^8}} \over {2 \times {{10}^8}}} = 1.5$$
$${\mu _B} = {{3 \times {{10}^8}} \over {1.5 \times {{10}^8}}} = 2$$
For TIR
$$\theta > {i_c}$$
$$\theta > {\sin ^{ - 1}}\left( {{{1.5} \over 2}} \right)$$
$$\theta > {\sin ^{ - 1}}\left( {{3 \over 4}} \right)$$
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