Show that the focal length of a thin lens is not changed when the lens is rotated so that the left and the right surfaces are interchanged.

Answer

A

Explanation

`1/(f_1)=(mu-1)(1/(+R_1)-1/(-R_2))……(i)`
`1/(f_2)=(mu-1)(1/(+R_1)-1/(-R_2))……(ii)`
Solving these two equations, we can see that
`f_1=f_2`