The apparent depth of water in cylindrical water tank of diameter `2R cm` is reducing at the rate of `x cm // min ` when water is being drained out at a constant rate. The amount of water drained in `c.c.` per minute is `(n_(1)=` refractive index of air, `n_(2)=` refractive index of water )

Options

A. `x pi R^(2) n_(1)//n_(2)`
B. `x pi R^(2) n_(2)//n_(1)`
C. `2 pi R n_(1)//n_(2)`
D. `pi R^(2) x`

Answer

b