Question

A fish is a little way below the surface of a lake. If the critical angle is ${49}^o,$ then the fish could see things above the water surface within an angular range at ${\theta }^o$ where

• A. $\theta ={49}^o$
• B. $\theta ={90}^o$
• C. $\theta ={98}^o$
• D. $\theta =24{\frac{1}{2}}^o$

Answer 1

Answer: (C)

Given: A fish is a little way below the surface of a lake. If the critical angle is ${49}^o$, then the fish could see things above the water surface within an angular ring at ${\theta }^o$

To find the value of $\theta$

Solution:

From the given figure it is clear that,

angular range is twice the critical angle.

Critical angle, ${\theta }_c={49}^{\circ }$

Therefore, $\theta =2\times {\theta }_c⟹\theta =2\times {49}^{\circ }⟹\theta ={98}^{\circ }$