Question

(c)
Calculate the focal length of a lens, if its power is - 25 D.
OR​

Answer 1

Answer:

The answer will be -0.04 .

Explanation:

We have given that;

                                  P = -25 D;

Now according to the formulae;

                                     P = 1 / f

  Now, put all the given value in the formulae;

Hence,                           -25 = 1 / f;

                                        f  = 1 / -25;

                                        f = -0.04;

That's all

Answer 2

Explanation:

p=1/f

-25=1/f

f=1/-25

= -0.04