Question

if a glass lens is immersed in oil what is the effect on focal length of lens​

Answer 1

here your answer!!!

hope its help you....

Answer 2

Given: A glass lens immersed in oil.

To find: Effect on focal length of lens

Explanation: Let the refractive index of lens be ug and refractive index of oil be uo.

The formula for focal length of lens is:

$\frac{1}{f} = ( \frac{ug}{uo} - 1)( \frac{1}{r1} - \frac{1}{r2} )$

where r1 and r2 is the radius of the two surfaces of the lens.

Now, when glass lens is kept in air the term ug/uo becomes smaller as compared to 1. Therefore, the term becomes negative. So, the lens starts showing opposite properties. The convex lens which has a positive focal length becomes negative(diverging) and concave lens which has negative focal length becomes positive(converging) .

Therefore, the properties of glass lens change from diverging to converging and vice versa when it is immersed in oil.