Question

Concave lenses are also known as
A) Converging lenses
B) Diverging lenses
C) Plane lenses
D) Circular lenses

Answer 1

Hint: A lens is an optical instrument that focuses or disperses a ray of light through the process of refraction. A simple lens consists of a single piece, while a compound lens can be said to comprise several simple lenses usually arranged along a common axis. Lenses are made from materials such as glass or plastic and are ground and polished or moulded to the desired shape. Converging lenses, as the name suggests, converge a parallel beam of light to a point. Similarly, diverging lenses diverge or spread a parallel beam of light.

Complete solution:
As discussed above, a concave lens curves inwards. It is a diverging lens, which implies that it spreads out light rays that have been refracted through it. A concave lens is thinner in the middle than at its ends. After light rays have passed through the lens, they seem to be coming from a point called the principal focus. The image formed by a concave lens is a virtual image, which means that it will appear to be further away than it is, and smaller than the object itself.

Hence we can say that the concave lens is also known as a diverging lens and the correct option is (B).

Note: Concave lenses are employed in telescopes and binoculars to enlarge objects. Concave lenses are most commonly used to correct myopia which is also called near-sightedness. Peepholes, better known as door viewers are security devices that give a wide angled view of objects outside the doors.