An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained ? Find the size and the nature of the image.

Explanation

Object distance,u=-27cm
Object height, h=7cm
Focal length, f=-18cm
According to the mirror formula
`1/v-1/u=1/f`
`v=1/f-1/u`
`(-1)/(18)+1/(27)=(-1)/(54)`
`v=-54cm`
The screen should-be placed at a distance of 54 cm in front of the given mirror.
Magnification, `m=("Image distance")/("Object distance")=(-54)/(27)=-2`
The negative value of magnification indicates that the image formed is real.
Magnification, m`=("Height of the image")/("Height of the Object")=(h_1)/h`
`h.=7xx(-2)=-14cm`