Question

the focal length of a concave lens is 13.3cm .Calculate its power.​

Answer 1

Answer:

The focal length of the concave lens = -13.3 cm = -0.133 m.

[The focal length of concave lens is always negative.]

We know that, P = 1/f.

Hence, P = 1/-0.133

⇒ P = -7.51 D

More Information -

Power is said to be the reciprocal of focal length in m.

Dioptre is the unit of power of lens.

1 dioptre is the power of a lens whose focal length is 1 metre.

Hence, 1 D = 1 m^{-1}.

The power of convex lens is positive.

And, the Power of concave lens is negative.