Question

What is the nature of lens if the power is zero

Answer 1

Answer

Power of lens is defined as the reciprocal of the focal length of the lens expressed in meter.

SI unit of power is Dioptre denoted by D.

Focal length of first lens f

1

=40 cm=0.4 m

Since the focal length is positive, so it is a convex lens.

Power of lens P

1

=

f

1

1

=

0.4

1

=2.5 D

Focal length of second lens f

2

=−20 cm=−0.2 m

Since the focal length is negative, so it is a concave lens.

Power of lens P

2

=

f

2

1

=

−0.2

1

=−5 D

Answer 2

Answer: It acts as a plane sheet of glass

Explanation: When power of a lens is 0D, it loses the ability to converge or diverge the light rays coming from an object. This generally happens when a convex lens and a concave lens of same focal lengths are combined or joined together.