A convex lens has focal length of 30cm. Calculate at what distance should the object be placed from the lens so that it forms at 60 cm on the other side of the lens ? Find the magnification produced by the lens in this case.

Explanation

Here, `f =30cm , u=? , v=60cm , m=?`
As `(1)/(f) = (1)/(v) - 1/u, :. 1/u = (1)/(v) - (1)/(f) = 1/60 - 1/30 = (1-2)/(60) = -1/60` or `u = -60cm`
Thus , `m =( h_(2))/(h_(1)) = v/u=60/-60 = -1`
Negative sign of m indicates that image is inverted.