Question

a lens having focal length f is cut into two parts and they are placed as shown in the figure what will be the effective focal length of the combination​

Answer 1

Answer:

f

Explanation:

when the lens is cut into two parts then the radius of lens does not changes

so the focal length will be,

       1/f=(u-1)(1/r-1/R)[by lens makers formula]

as the radius doesnot changes the focal length remains same

Answer 2

Answer:

Let effective focal length be F,

1/F = 1/f + 1/f =2/f

F =f/2