Question

Two lenses of power +5 D and -7 D are in contact with each other. Find out the power of the combination of the lenses. Combined lens will be convex or concave?
Solution:
Given, P1 = +5 D; P2 = -7 D; P = ?
∴ The power of combination of the lenses
∴ P = P1 + P2
= +5 D – 7 D
or P = – 2D
∵ As power is negative, so combination will be diverging or concave.

Answer 1

Explanation:

lenses in contect then the resultant power of combination will be the sum of powers of all lenses. so the power of given combination is -7 + 5= -2D. because power is negative so it is of diverging in nature.