Question

what is the focal length of a lens whose power is + 1.5 d

Answer 1

Explanation:

power of the lens = 1/ f in m

1.5 =1/f

f= 1/1.5

=10/15

0.6 m or 60 cm.

the person is suffering fm hypermetropia.

Answer 2

Answer:

$Given, \: \: \: \: \: \: \: \: \: \: P = 1.5 D = \frac{3}{2} D$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ƒ = ?$

$Using \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ƒ = \frac{1}{p}$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ƒ = \frac{1}{ \frac{3}{2} } = \frac{2}{3} m$

$⇒ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ƒ = \frac{2}{3} \times 100 = \frac{200}{3}$

$∴ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ƒ = 66.6cm$