Question

The power of the lens is +2.5D.
Its focal length (in cm) will be:
(a)+40
(b) -40
(c)-80
(d)+80
​

Answer 1

Answer:

option (a) +40cm

Explanation:

Given:

P = 2.5 D

To find:

focal length of the lens.

Formula Used:

Focal length = 100/P (cm)

Solution:

f = 100/2.5 = +40cm