Question

Find the focal length of concave lens having power 0.3D

Answer 1

Given:-

• Power of lens (P) = 0.3D

To Find:-

• Focal length (f)

Solution:-

As we know that Power of the lens is defined as the reciprocal of its focal length.

→ Power = 1/focal length

→ P = 1/f

Substitute the value we get

→ 0.3 = 1/f

→ f = 1/0.3

→ f = 10/3

→ f = 3.33 cm

∴ The focal length of the concave lens is 3.33 cm.

Answer 2

Given :-

• Power of concave lens = 0.3D

To Find :-

• The focal length of convave lens.

Solution :-

☀ Finding Focal length of Concave lens. ☀

As we know that,

↪ P = 1/f ( Here, P is Power and f is Focal length. )

↪0.3 = 1/f

↪f = 1/0.3

↪f = 3.33cm.

☀ Some formulae related to mirror. ☀

• Mirror formula :- 1/v + 1/u = 1/f

• Magnification :- m = -v/u