A rod of length 10 cm lies along the principal axis of a

A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is :

The focal length of the mirror

-	1	=	1	+	1
	f		v		u

For A end of the rod the image distance When u₁ = – 20 cm

⇒ -	1	=	1	-	1
	10		v₁		20

	1	=	-1	+	1	=	-2 + 1
	v₁		10		20		20

v₁ = – 20 cm
For when u₂ = – 30 cm

	1	=	1	-	1
	f		v₂		30

	1	=	-1	-	1	=	-30 + 10	=	-20
	v₂		10		30		300		300

v₂ = – 15 cm
L = v₂ – v₁ = – 15 – (– 20)
L = 5 cm