What is a periscope and where is it used?

Here are the answers to your questions:

1. A periscope is used to see objects that are obstructed from direct view, such as looking over a wall or from inside a submarine.

2. In day-to-day life, periscopes are used in submarines to see above the water's surface, and also in tanks to allow the crew to observe their surroundings from inside the vehicle. They can also be found in some children's toys or for looking over crowds at events.