Question

the person who wants to read a book placed at 20 CM there near point of his eyes is 30 cm calculate the power of a lens required​

Answer 1

he require lens of power 1.5D

Answer 2

-1.67 D. The provided information over here can be represented as follows.

u = -20 cm, v = -30 cm, we have to find P from the given information. By using the focal length formula, we know that, f = (uv)/(v-u).

Now, if we substitute the values in this formula, we get f = {(-20)(-30)}/ (-30+20) = -60 cm.

Therefore, now we can find the power easily by using the formula, P = 100/f.

We know that value of f, which is -60 cm. Hence, P = -(100/60) = -1.67 D.