A concave mirror forms an image of 20 cm high object on a screen placed 5.0 m away from the mirror. The height of the image is 50 cm. Find the focal length of the mirror and the distance between the mirror and the object.

Answer

A, B, C, D

Explanation

Given that `h_1=20 dm`
v=-5m=-500cm`
`since (-v)/u=h_2/h_1`
or `500/u=50/20`
(becau7se the image is inverted)
`or y=-500xx2/5`
=`200cm=-2m`
`1/v+1/u=1/f`
or `1/(-5)+1/(-2)=1/f`
or `-1/f=7/10`
or f=-10/7=-1.44`
`so the focal length is 1.44 m.