State the number of images of an object placed between the two plane mirrors, formed in each case when the mirrors are inclined to each other at (a) 90° and (b) 60°

(a) When two mirrors are kept perpendicular to each other i.e., θ = 90°,

then n = 360º\over 90º = 4

n = 4, is even so the number of images is n – 1

Therefore,

n – 1 = 4 – 1 = 3

(b) When two mirrors are kept at 60° to each other,

then n = 360º\over 60º = 6

n = 6, is even so the number of images is n – 1,

Therefore,

n – 1 = 6 – 1 = 5

Hence, for two mirrors kept at 60° to each other, five images are formed for an object kept in between them.