Question

what is the nature of the lens right answer​

Answer 1

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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