Login/Sign Up
Home » A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of 60 cm 40 cm
A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of 60 cm 40 cm
Physics | Physics
A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of 60 cm 40 cm

(1) 20 cm from the lens, it would be a real image
(2) 30 cm from the lens, it would be a real image
(3) 30 cm from the plane mirror, it would be a virtual image
(4) 20 cm from the plane mirror, it would be a virtual image

Solution: Answer (4)

Using lens formula for the first refraction from convex lens, we can write:

I1 here is the first image by a lens. The plane mirror will produce an image at a distance 20 cm to the left of it.
For the second refraction from the convex lens,
u = –20 cm, v = ? , f = 30 cm

By making use of the lens formula, we get v = – 60 cm. Thus the final image is virtual and at a distance,
60 – 40 = 20 cm from plane mirror.

 

i

More Material