1. It is an instrument used for viewing bodies or ships, which are over and around another body or a submarine.
2. It is based on the principle of the law of reflection of light. It consists of a long outer case and inside this case mirrors or prisms are kept at each end, inclined L’9ht at an angle of 45°.
3. Light coming from the distant body, falls on the mirror at the top end of the periscope and gets reflected 450 vertically downward.
4. This light is reflected again by the second mirror kept at the bottom, so as to travel horizontally and reach the eye of the observer.
5. In some complex periscopes, optic fibre is used instead of mirrors for obtaining a higher resolution.
6. The distance between the mirrors also varies depending on the purpose of using the periscope.
