Question

In this experimental setup the combination of concave lens and convex lens separated by a distance d behaves as a single lens of focal length f

Answer 1

The focal length f of the combination will decreases.

• As given that the combination of concave lens and convex lens are separated by distance d and having focal length f
• Let the focal length of the concave lens be f₁ and focal length of convex lens be f₂
• Let the focal length of the combination be f₃.
• Now finding the relation
• 1/f₃=1/f₁+1/f₂-d/f₁f₂
• As they are in contact d=0
• Therefore 1/f₃=1/f₁+1/f₂