A periscope is a type of visible device that can be used by a person in a secret location to observe a specific target. Usually the main components of this device are - mirrors , eye-catching lenses , external or physical infrastructure with the necessary path to reach the light. It is necessary to determine at least two straight 450 angular positions to reach the light. The mirror at the top receives light and sends it to the lower mirror. With the help of a periscope, an observer makes the necessary decisions. World War I was used in experiments for this purpose. Members of the military used periscope in tanks and armored vehicles. During wartime, it is used to ensure the position of the opponent from inside the submarine or test. The periscope used in submarines is quite complex in nature. The position of the object is confirmed by a set of lenses , two telescopes and a prism instead of a mirror. The periscope used in modern submarines is simpler with two telescopes mounted on either side. If for some reason the two telescopes are different , then the differences between them are made workable by narrowing them down.