How many plane mirrors are used in a periscope and kaleidoscope ?
(a) 2 and 3 respectively
(b) 3 each
(c) 3 and 2 respectively
(d) 2 and 4 respectively

(a) 2 and 3 respectively

Reason — In a periscope two parallel plane mirrors each inclined at 45° with the vertical walls are placed facing each other. In a kaleidoscope three plane mirrors inclined with each other at 60° are used.