Question

One student uses a lens of focal length 50cm and the other of focal length -50cm.What is the nature of the lens and its power used by each of them?

Answer 1

Answer:

If the focal length is in positive value it is convex lens & if it is negative it is concave lens.

So, the lens of -50cm focal length is a concave & the other one is convex lens.

Powers

1). f=-50cm= -0.5m

p= 1/f = 1/(-0.5) = -10/5

p= -2D

2). f= 50cm = 0.5m

Similarity, it's also 2D but it is positive, as minus is not here.