Question

The power of a lens is +2.5 D. What kind of lens it is and what is its focal length?

• A. 40cm, Convex lens
• B. 30cm, Convex lens
• C. 400cm, Concave lens
• D. 400cm, Convex lens

Answer 1

The correct option is A 40cm, Convex lens

we know that power $P=2.5D$

$P=\frac{1}{f}$

$f=\frac{1}{2.5}=0.4m=40cm$

Since the focal length of lens is positive so it is a convex lens. It is a converging lens.