Determine the focal length of a thin converging lens if the power is 5.0 dioptres?

A. 0.1 m
B. 0.2 m
C. 2.0 m
D. 2.5 m

Correct Answer:

Option B – 0.2 m

Explanation

Power of a lens = 1/f

f = focal length

f = 1/p = 1/5

= 0.2m