Question

Why is a concave lens also called a diverging lens?

Answer 1

Concave lenses are thinner at the middle. Rays of light that pass through the lens are spread out (they diverge). A concave lens is a diverging lens. When parallel rays of light pass through a concave lens the refracted rays diverge so that they appear to come from one point called the principal focus.

Answer 2

light falling on the concave lens is bent outwards. so,a concave lens is also known as diverging lens.