JEE Main Online Paper (Held On 19 May 2012)
A) \[\sin \theta >\frac{5}{9}\]
B) \[\sin \theta >\frac{2}{3}\]
C) \[\sin \theta >\frac{8}{9}\]
D) \[\sin \theta >\frac{1}{3}\]
Correct Answer: C
Solution :
For total internal reflection on face AC \[\theta >\] critical angle (C) and \[\sin \theta \ge \sin C\] \[\sin \theta \ge \frac{1}{{{w}_{{{\mu }_{g}}}}}\] \[\sin \theta \ge \frac{{{\mu }_{w}}}{{{\mu }_{g}}}\Rightarrow \sin \theta \ge \frac{\frac{4}{3}}{\frac{3}{2}}\] \[\therefore \]\[\sin \theta \ge \frac{8}{9}.\]
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