Question

What is the working principle, construction and application of periscope?

Answer 1

Periscope :

1. It is a tubular optical instrument that allows objects that are not in direct line of sight to be viewed.
2. The simplest type of periscope consists of a tube at the ends of which are two mirrors, parallel to each other but at 45° to the axis of the tube.
3. This device produces no magnification and does not give a cross line image.
4. The arc of vision is limited by the simple geometry of the tube: the longer or narrower the tube, the smaller the field of view.

Working :

1. It works on the law of reflection.
2. The law of reflection states that the light from the object falls on one mirror at $45°$from the object and is reflected, this reflected light then falls on another mirror and is again reflected until it reaches the human eye.

Construction :

1. It can be constructed by using a pair of flat mirrors or prisms and a rectangular hollow tube that has a viewing window at the top and bottom of the tube.
2. The mirrors within this structure are fixed at an angle of $45°$ at the two ends of the rectangular hollow.

Application :

1. It is used in submarines for general navigation and detection.
2. It is used on battlefields to look out of trenches safely without exposing the observer's body.
3. It is used in a nuclear reactor to observe the chemical reaction.

An illustrative diagram of periscope :