A convex lens is held `45 cm` above the bottom of an empty tank. The image of a point at the bottom of a tank is formed `36 cm` above the lens. Now, a liquid is poured into the tank to a depth of `40 cm.` It is found that the distance of the image of the same point on the bottom of the tank is `48 cm` above the lens. Find the refractive index of the liquid.

Answer

A, C

Explanation

Using lens formula,
`1/36-1/(-45)=1/f`
`:. f=20 cm`
In the second case, let `mu` be the refractive index of
the liquid, then
`1/48-1/(-(5+40/mu))=1/20`
Solving this, we get `mu=1.37`