(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.