Question

A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is $\frac{4}{3}$ and the fish is 12 cm below the surface. The radius of this circle is

• A. $36\sqrt{7}cm$
• B. $\frac{36}{\sqrt{7}}$
• C. $36\sqrt{5}$
• D. $4\sqrt{5}$

Answer 1

The correct option is B $\frac{36}{\sqrt{7}}$

$r=\frac{h}{\sqrt{{\mu }^2-1}}=\frac{12}{\sqrt{\frac{16}{9}-1}}=\frac{36}{7}cm$