Question

a person wants to read a book placed at 20 cm wheras the near point of his eye is 30 cm.calculate the power of lens required.

Answer 1

-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.

Answer 2

Explanation:

• u is -20cm
• v is -30cm
• f is uv/v-u
• -20*-30/-30-(-20)
• -60cm

• p is 100/f
• 100/-60
• -1.67