Question

The focal length of a lens is 50 cm. Its power would be ______.

विकल्प

• 50 dioptres

• 2 dioptres

• 20 dioptres

• none of these

Answer 1

The focal length of a lens is 50 cm. Its power would be 2 dioptres.

Explanation:

Power is given by $$P = \frac{100}{f\text{ (in cm)}} = \frac{100}{50} = 2\text{ dioptres}$$.

The other values arise from incorrect formulas or incorrect unit conversions.