Question

plz ans it...............​

Answer 1

given, focal length of convex lens, f1 = +25cm or +0.25m

so, power of convex lens , P1 = 1/f1 = 1/0.25m = +4D

again, focal length of concave lens, f2 = -10cm or -0.1m

so, power of concave lens, P2 = 1/f2 = 1/-0.1m = -10D

• now when the concave and convex lenses are placed in contact with each other then, power of system will be sum of power of concave lens and convex lens.

e.g., P = P1 + P2

or, P = +4D - 10D = -6D

hence, power of combination is -6D