We combined a convex lens of focal length `f_(1)` and concave lens of focal lengths `f_(2)` and their combined focal length was F . The combination of these lenses will behave like a concave lens, if

Options

A. `F_(1) gt f_(2)`
B. `f_(1) lt f_(2)`
C. `f_(1) = f_(2)`
D. `f_(1) le f_(2)`

Answer

A

Explanation

For combinatio of one convex and one concave lens
`(1)/(F)=(1)/(f_(1))-(1)/(f_(2))rArr F=(f_(1)f_(2))/(f_(2)-f_(1))`
If `f_(1)gt f_(2)`, then F will be negative.