Question

What is mean by periscope?​

Answer 1

Answer:

A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position.

2 mirrors, one at the top and another at the bottom, are placed at 45° to make it work

Answer 2

an optical instrument for viewing objects that are above the level of direct sight or in an otherwise obstructed field of vision, consisting essentially of a tube with an arrangement of prisms or mirrors and, usually, lenses: used especially in submarines.