Question

how are two mirrors placed in a Periscope ?

Answer 1

Two mirrors in a periscope are placed at an angle of 45° to each other. These mirrors are also placed parallel to each other.

A periscope is used to observe an obstacle or condition through, around, or over an object. This obstacle prevents direct line-of-sight observation from the current position of an observer. Periscopes can be either simple or complex. Simple ones make use of mirrors while complex ones have prisms in their place.

Answer 2

Periscope is an optical instrument which is used to observe what is going on the surface of water in the submarines.
It is also used for observation purpose in trenches of world war.

Principle of working:
Reflection of light.

In simple periscope, two mirrors are placed at an angle 45 degrees.

Working principle:
Parallel rays fom distant object fall on first mirror and gets reflected at same angle and they are made to incident second mirror and again parallel rays are reflected to our eyes by which we can see.