An object is placed at a distance of 20 cm from the pole of a concave mirror of focal length 10 cm. The distance of the image formed is

Options

A. `+20` cm
B. `+10` cm
C. `-20` cm
D. `-10` cm

Answer

C

Explanation

Here , as per the Cartesian sign convention, Object distance , u = - 20 cm
Focal length of the mirror , f = -1 0 cm
According to mirror formula
`1/u+1/v=1/f:.1/v=1/f-1/u=1/(-10)-1/(-20)`
or `1/v=1/(-10) +1/20 =(-2+1)/20=-1/20`
or `v=-20cm`