Question

A fish looks outside water. It is situated at a depth of 12 cm below water surface. if the refractive index of water is 4/3 then radius of the circle through which it can see will be

• A. $12\times \frac{3}{\sqrt{7}}cm$
• B. $12\times 3cm$
• C. $12\times 3\sqrt{5}cm$
• D. $12\times \frac{\sqrt{5}}{3}cm$

Answer 1

The correct option is A $12\times \frac{3}{\sqrt{7}}cm$

As shown in the figure it can see an conical view with cone angle ${\theta }_c$ (critical angle)

${\theta }_c=si{n}^{-1}\frac{1}{\mu }=si{n}^{-1}\frac{3}{4}$

$R=12tan{\theta }_c=12\times \frac{3}{\sqrt{7}}$.