Question

A convex lens of power 20 D and a concave
lens of power 15 D are placed in contact with
each other. The focal length of the equivalent
lens will be​

Answer 1

Answer:

P = P1+P2

P = 1/F

Explanation:

P = 20-15 = 5 D

F = 1/P

= 1/5 = 0.2 m

Answer 2

Explanation:

P = P(convex) + P(concave)

= 20 + ( -15 )

P = 5

P = 1/f

f = 0.2