Question

The power of a lens is +2.0D. Its focal length should be (a) 100 cm
(b) 50 cm
(c) 25 cm
(d) 40 cm

Answer 1

$\huge\mathbb{SOLUTION}$

${p=}$$\frac{100(in cm)}{f}$

${2=}$$\frac{100}{f}$

${f=}$$\frac{100}{2}$

${f=50cm}$

Answer 2

The power of a lens is +2.0 D. Its focal length should be 50 cm.

Explanation:

The lens has the power +2.0 D. It’s focal length must be 50 cm.

Lens power is equal to the focal length’s reciprocal in meters. This is shown by the equation as

                            $P = \frac{1}{f}$

    So, focal length $= \frac{1}{Power}$

                            $f = \frac{1}{2}$

Thus focal length f = 50 cm.

The focal length is calculated as 50 cm.

Therefore the correct answer is Option (b)50 cm