A man stands 10 m in front of a large plane mirror. How far must he walk before he is 5 m away from his image?
The object distance is equal to image distance in a plane mirror.
For the distance of man from his image to be 5m-
The distance of man from mirror+ distance of image from the mirror= 5m
Since object distance= image distance
Therefore, 2*distance of man from the mirror= 5m
Distance of man from the mirror= 5/2 = 2.5m
The man is 10m from the mirror at the starting, so he will have to walk 10 – 2.5 =7.5m towards the mirror for being 5m away from his image.