CBSE Class 10 Answered

Figure shows the periscope setup to view the object at the other side of opaque wall.

The object viewed by the observer not at the line of sight.

Periscope consists of a tube that has two plane mirrors at end .

Plane mirrors are oriented inside the tube so that plane of mirror is at 45^o with axis of tube and the

reflecting side of mirrors are facing each other. Tube has openings in front of mirrors so that light ray from 

object incient on one mirror and reflected light from other mirror is viewed by observer .

Light ray from object incident on plane mirror with angle of incidence 45^o .

By law of reflection, angle of reflection for reflected ray is 45^o .

Hence light ray from the object bends 90^o and incident on other mirror as shown in figure.

The reflected ray from first mirror is reflected by second mirror so that the ray turns again 90^o and viewed by observer .

Periscope is used in submarine and defence to view and aim the enemy at same time protect the soldiers.

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Figure shows the usage of convex mirror as rear view mirror in vehicles .

Unlike plane mirror , magnification of image by convex mirror is less than one.

Hence person driving the vehicle has wide view of  road in back side