1) A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of these circles (in cm) is A) $36\sqrt{5}$ B) $4\sqrt{5}$ C) $36\sqrt{7}$ D) $\frac{36}{\sqrt{7}}$ Answer: Option DExplanation:$\sin i_{c}=\frac{1}{\mu}=\frac{r}{\sqrt{r^{2}+h^{2}}}$ using h=12 cm, $\mu$ =4/3 we get r= $\frac{36}{\sqrt{7}}$
