A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a
A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a
A. convex mirror of focal length 10 cm
B. concave mirror of focal length 40 cm
C. concave mirror of focal length 60 cm
D. concave mirror of focal length 10 cm
6 views
1 Answers
Correct Answer - A
(a) Power, `P=2P_(L)+P_(M)`
or `-1/F=2(-1/0.2)+0orF= 10cm`
On silvering the surface of the lens, it behaves as a mirror.
Therefore, the combination behaves as a convex mirror of focal length 10 cm.
6 views
Answered