Question

The power of a lens of focal length 20 cm is

• A. 5 D
• B. 0.2 D
• C. 1 D
• D. 2 D

Answer 1

The Correct Option is A

The power of a lens is the reciprocal of its focal length in meters. 

Power (P) = 1 / focal length (f) The focal length is given as 20 cm. 

First, we need to convert the focal length to meters: f = 20 cm = 20/100 m = 0.2 m 

Now, we can calculate the power of the lens: P = 1 / f = 1 / 0.2 = 5 D 

Therefore, the power of the lens is 5 D.