Question

A convex lens of power 5D and a concave lens of power 7.5 D are placed in contact
with each other.
(a) power of this combination of lenses?
(b) focal length of this combination of lenses?​

Answer 1

Answer:

12.5 D

Explanation:

P=p1+P2

In question 2 you can use formula

P=1/f

Answer 2

Answer:- (a) -2.5 D

(b) -40 cm