An object is placed at a distance of 30 cm from a concave mirror and its real image is formed at a distance of 30 cm from the mirror. The focal length of the mirror is

Options

A. 15 cm
B. 45 cm
C. 30 cm
D. 20 cm

Answer

A

Explanation

Given, `u =-30 cm`
`v=-30 cm`
Using relation, `(1)/(f)=(1)/(v)+(1)/(u)`
`(1)/(-30)+(1)/(-30)=(1)/(f)`
`therefore " "` Focal length of the mirror, `f=-15 cm`