How can we find the angle formed between two plane mirrors if the number of images formed is given?

When two plane mirrors are placed edge to edge at an angle to each other, multiple virtual images are formed. 

The number of images formed by two plane mirrors at an angle is given by this formula:

number of images = where  is the angle formed by the two mirrors. 

Rearranging this equation gives a formula for the angle:

 = 360/(number of images -1)

The smaller the angle between the mirrors, the more images that will be formed. If the mirrors are parallel an infinite number of images will be formed. You've probably observed this in a room with mirrors on opposite walls, such as a department store dressing room. You can see the effect of changing the angle if you have two flat mirrors.