Two thin lenses of focal length `f_(1)` and `f_(2)` are in contact and coaxial. The power of the combination is

Options

A. `(f_(1)+f_(2))/(2)`
B. `(f_(1)+f_(2))/(f_(1)f_(2))`
C. `sqrt((f_(1))/(f_(2))`
D. `sqrt((f_(2))/(f_(1))`

Answer

B

Explanation

`P=P_(1)+P_(2)=(1)/(f_(1))+(1)/(f_(2))`
`F=(f_(1)+f_(2))/(f_(1).f_(2))`