An object is placed at a distance of `1.5 m` from a screen and a convex lens is interposed between them. The magnification produced is `4`. What is the focal length of the lens ?

Options

A. `1m`
B. `0.5 m`
C. `0.24 m`
D. `2 m`

Answer

C

Explanation

Here, `m = (v)/(u) = - 4` or ` u = (-v)/(4)`
Also, `|u| + |v| = 1.5`
`v/4 + 5 = 1.5` or `v = 1.2 m` and `u = (-1.2)/(4) = -0.3 m`
`:. f = (uv)/(u- v) = (-0.3 xx 1.2)/(-0.3 xx 1.2) = 0.24 m`