Question

1. Doctor advised to use 2D lens. What is its
focal length ?
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Answer 1

Answer:

Focal length = 1/P = 1/2 = 0.5 cm.

Type of Lens : Convex.

Answer 2

Given:-

• Power of lens (P) = 2D

To Find:-

• Focal Length (f)

Solution:-

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

Si unit of Power of lens is dioptre (D)

→ P = 1/f

substitute the value we get

→ 2 = 1/f

→ 2×f = 1

→ f = 1/2 m.

→ f = 0.5m

∴ The Focal length of the lens is 0.5 m