Question

A myopic person has a power of -1.25 Dioptre. What is the focal length and nature of his lens?

• A. 50 cm and convex lens
• B. 80 cm and convex lens
• C. 50 cm and concave lens
• D. 80 cm and concave lens

Answer 1

The correct option is D 80 cm and concave lens

Focal length of the lens $f=\frac{1}{Power}$
$\therefore$ $f=\frac{1}{-1.25}=-0.8m=-80cm$
Since focal length of the lens is negative, thus the lens is a concave lens.