Question

A light wave enters from I medium into II medium. Its velocity in second medium is double that in I medium. For the phenomenon of total internal reflection to take place the angle of incidence must be greater than a certain value. This value is

• A. ${20}^0$
• B. ${30}^0$
• C. ${45}^0$
• D. ${60}^0$

Answer 1

Answer: (B)

${30}^0$

$V_{II}=2V_I$ from this, II medium is optically rarer medium than I medium.

Hence, ${}^I{\mu }_{II}=\frac{1}{sinC}=\frac{V_{II}}{V_I}$

$\Rightarrow \frac{1}{sinC}=2$

$sinC=\frac{1}{2}\left(or\right)C={30}^0$.