The given lens is broken into four parts rearranged as shown. If the initial focal length is f, then after rearrangement the equivalent focal length is

Options

A. f
B. `f//2`
C. `f//4`
D. `4f`

Answer

b.

Explanation

Cutting a lens in transverse direction double their focal length, i.e., 2f.
Using the formula of equivalent focal length,
`(1)/(f)=(1)/(f_(1))+(1)/(f_(2))+(1)/(f_(3))+(1)/(f_(4))`
We get equivalent focal length as `(f)/(2)` .