Question

A concave lens is commonly called
(A). Converging lens
(B). Diverging lens
(C). Normal lens
(D). Tangent lens

Answer 1

Hint: You can start by explaining all the options given in the problem. Then take an example of a concave lens with two incident rays perpendicular to the principal axis and draw a diagram representing this situation. Then look at the rays that were refracted by the concave lens and determine the nature of the lens.

Complete step-by-step answer:
When the light rays bend towards each other after refraction through a lens then the lens is converging.
When the light rays bend away from each other after refraction through a lens then the lens is diverging.
When the light rays do not get refracted after refraction through a lens then the lens is normal.
The tangent lens does not exist.
To understand what kind of lens a concave lens is, let’s draw a ray diagram of a concave lens with two incident rays parallel to the principal axis.
The ray diagram will be as follows

As you can see whenever incident rays are parallel to the principal axis then a virtual image will be formed at the focus of the concave lens.
But our main focus is not the virtual image but the refracted rays of light. As you can see that the rays of light are getting farther and farther away from each other, which means that they are diverging.
So, the concave lens behaves as a diverging lens.
Hence, option B is the correct choice.

Note: In the solution discussed above we took an example of two incident rays that were parallel to the parallel axis. You can also take incident light rays that are not parallel to the principal axis to create your version of this solution, any incident rays will work to show the diverging nature of concave lenses.