CBSE Class 6 Answered

The figure shows a tree behind a  high wall which we canno see direclt. We can, however, see this treee by using a periscope as follows:The upper hole of periscope is turned towards the object to be seen (here a tree) so that mirror M₁ faces the object. And we look into the periscope from the bottom hole in front of lower mirror M₂.  The light rays coming from the tree fall on the plane mirror M₁. Mirror M₁ reflects these rays of light towards the mirror M₂. The mirror M₂ then reflects the light towards the eye of the person looking into periscope through the lower hole. Since the light rays coming from the tree enter the eye, it is possible to see the image of the tree in the lower mirror M₂ (even though the tree cannot be seen directly).