Answer the following questions.

Why are the two mirrors in a periscope placed parallel to each other?

In a periscope, two mirrors are placed at an angle of 45 degrees and at the maximum distance. Due to maximum distance between the mirrors, multiple images do not form and light from the object strike the first mirror and its image is formed. This image of first mirror becomes an object for the second mirror and as they are parallel, light from the first mirror gets incident on the second mirror at right angle and the same image is thus formed. Therefore, the mirrors are kept parallel to each other.