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Question
Describe the principle of simple periscope through an outline ray diagram. Give one of its uses.
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Solution
Simple periscope is based upon the principle of reflection. It consists of cardboard or wooden tube, bent twice at right angles, and is provided with two openings as shown in the figure. Two plane mirrors are fixed at the bends of the tube at an angle 45° to the framework, such that the mirrors face each other. The tube is completely blackened from inside to avoid any reflection from its sides.
The parallel rays coming from an object at a higher plane, strike the plane mirror at an angle of 45° and hence are reflected through an angle of 45°.
These reflected rays strike the second mirror at an angle of 45° and hence are further reflected through an angle of 45°. These reflected rays on reaching the eye from the image on retina.
Use of periscope: It is used by soldiers in trench warfare.
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