Question

A tank having cross sectional area A has a hole at the bottom of area of cross section $\frac{A}{1000}$. Bottom of the tank is a plane mirror. The tank contains water of refractive index $\frac{4}{3}$. At the instant, when height of the water in the tank is 5m, a fish is rising vertically in the tank with a velocity $3\frac{cm}{sec}$ toward the surface.



The velocity of the fish as observed by the observer looking directly at the fish is

• A. 2 $\frac{cm}{s}$
• B. 3$\frac{cm}{s}$
• C. 4$\frac{cm}{s}$
• D. 1$\frac{cm}{s}$

Answer 1

The correct option is A 2 $\frac{cm}{s}$

Velocity of fish w.r.t surface in air $\frac{3+1}{\mu }=3\frac{cm}{s}$



Velocity as viewed directly by the observer $=3-1=2\frac{cm}{s}$