Question

A concave mirror has a focal length of 20 cm and object is placed at a distance of 16 cm from it find the position and the nature of image formed by it. What will be the position of nature of image if the concave mirror is replaced by a convex mirror of the same focal length..

Answer 1

Answer:

A.)concave mirror:-

Focal length=20cm

object is placed at a distance=16cm

position if image=?

MIRROR FORMULA=1/F=1/V+1/U

THEN,

1/20=1/16+1/v

according to sin convention;

1/-20=1/-16+1/v

1/v=1/20-1/16

1/v=-4+5/80. (by l.c.m)

1/v=1/80

1/v=80cm

MAGNIFICATION =-V/U

=(-80)/-20

=4cm

Nature of image:erect,diminished,virtual.

B.)Convex mirror.

focal length =20cm

object is placed at a distance=16cm

position of image=?

MIRROR IMAGE=1/F=1/V+1/U

THEN,

1/20=1/v+1/16

according to sin convention;

1/20=1/v+1/-16

1/v=1/20+1/16

1/v=5+4/80

1/v=9/80

1/v=8.8cm

MAGNIFICATION =-V/U

=-8.8/-16

=1.8cm

NATURE OF IMAGE =ERECT,DIMINISHED,VIRTUAL