Question

How will be the change in focal length of a glass convex lens when it is immersed in benzene solution. The refractive index of water, glass and benzene are 1.33, 1.45,1.50 respectively

Answer 1

focal length decreases

Explanation:

As refractive index increases the focal length decreases

Answer 2

Answer:

In benzene it becomes a concave lens of focal length 27/20 times focal length in air

Explanation:

Let the focal length of the convex lens be 'f' in air or vaccum.

1st step- Take out the focal length of convex lens of radius of curvature 'R' by taking air as surrounding. Apply Lens maker formula and you will get focal length as

f(air) =10R/9 (check out 1st image)

2nd step-Take out the focal length of convex lens of radius of curvature 'R' by taking benzene as surrounding. Apply Lens maker formula and you will get focal length as

f(benzene ) =-3R/2 (check out 2nd image)

Negative sign suggests that it will be a concave lens.

Now take out ratio

So f(benzene) = 27/20 f(air)