Question

Power of a lens is -4D,then it's focal length is

Answer 1

Answer:

Explanation:

Formula :

power= 1 / focal length .

Given :

power = - 4 D

- 4 D = 1 / f

= > f = 1 / - 4

= > f = - 0.25 m

f=0.25m or 25cm

Answer 2

Answer:

The power of a lens is a measure of its ability to produce deviation of light. A lens of short focal length produces more deviation of light than that of a lens of larger focal length. So, power of a lens is defined as the reciprocal of its focal length. The unit of power of lens is dioptre, D where f is in meter.answer is -0.25m

Explanation:

because, the answer in the notes