Question

An object `2 cm` high is placed at a distance of `16 cm` from a concave mirror, which produces a real image `3 cm` high. What is thr focal length of the mirror ? Find the position of the image ?

Answer 1

Correct Answer - `f = -9.6 cm, v = -24 cm`
Here, `h_(1) = 2 cm, u = - 16 cm`,
`h_(2) = - 3cm` (`because` image is real and inverted)
As `(-h_(2))/(h_(1)) = (v)/(u)`
`:. V = (-h_(2))/(h_(1))u = (3)/(2) xx (- 16) = - 24 cm`
`(1)/(f) = (1)/(v) + (1)/(u) = (1)/(-24) - (1)/(16) = (- 2 - 3)/(48) = -(5)/(48)`
`f = -(48)/(5) = - 9.6 cm`