Question

What is power of lens and si unit one student uses a lens of focal lenth 50 and another is -50what is nature of lens and its power?

Answer 1

Given

focal length f₁ = 50 m and

focal length f₂ = - 50 m

We know power of lens is given by the expression P = (1/f)

P₁ = (1/50) =  0.02 D

As the power is positive, the nature of lens will be converging lens.

Again P₂ = (1/-50) = -0.02 D  

As the power is negative, the nature of lens will be diverging lens.