Question

A convex lens of focal length 10 cm is placed in closed contact with a concave lens of focal length 10 cm. What is The power of combination?

Answer 1

Answer:

20 cm

Explanation:

Given,

f¹=+10 cm

f²=-20 cm

The focal length of the combination is given by

1\f=1\f¹+1\f²

1/f=1/10+1/-20 = 1/20 cm

f=+20cm