A thin lens made of a material of refractive index `mu_(0)` has a focal length `f_(0)` in air. Find the focal length of this lens if it is immersed in a liquid of refractive index `mu`.

Options

A. `-(fn^(')(n-1))/(n^(')-n)`
B. `-(fn^(')(n-1))/(n(n^(')-n))`
C. `-(n^(')(n-1))/(f(n^(')-n))`
D. `(fn^(')n)/(n-n')`

Answer

A

Explanation

`(1)/(f)=((n-1)/(1))((1)/(R_(1))-(1)/(R_(2)))`
and `(1)/(f_('))=((n-n^('))/(n^(')))((1)/(R_(1))-(1)/(R_(2)))`
`:. (f^('))/(f)=(n-1)/(1)xx(n^('))/(n-n^('))impliesf^(')=-(fn^(')(n-1))/(n^(')-n)`