Question

An object is held at 30 cm in front of a convex mirror of focal length 15 cm. At what distance from the convex mirror should a plane mirror be held so that images in the two mirrors coincide with each other?

Answer 1

Here, `u = -30 cm, f=15cm`.
From `(1)/(v) + 1/u =(1)/(f)`, `(1)/(v)= (1)/(f) - 1/u = 1/15 + 1/30 = 3/30 = 1/10`
`v=10cm`.
Let the plane mirror be held at M so that images in two mirrors coinside

`:. MP = MI - PI=1/2OI - PI=1/2(30+10)-10 = 10 cm`.