Question

Which of the following is not the characteristic of a concave lens?
A) Thick at the edges and thin in middle
B) Used to correct short sightedness
C) A diverging lens
D) Used to correct long sightedness

Answer 1

Hint: The concave lens is the lens which diverges the light which is coming from the source of light to the diminished and virtual image. It has at least one surface curved from inside. Concave lens can form both virtual and real images.

Complete step by step answer:
The lens can be defined as an optical device which disperse the beam of light. This is done so that the refraction can occur. The simple lens has only one piece of transparent material whereas, the compound lens has several simple lenses. There are two types of lenses:
A) Convex lens – These types of lenses are thin at edges and thick in the middle. They are made up of two spherical surfaces. This lens is also known as a converging lens because it converges the straight beam of light. This lens is used to correct the defect of eye, hypermetropia or long sightedness. It is used as magnifying glass.
B) Concave lens – This type of lens diverges the ray of light coming from the source so, this lens is also known as diverging lens. They are thick at edges and thin in the middle. These are also used to cure the defect which is known as myopia or short sightedness because of its property of spreading of light.
Hence, the correct option is (D).

Note: The person who suffers from myopia has the eyeball too long which makes the images of faraway objects fall short of retina. So, these lenses spread out the light rays and correct the shortfall before it reaches the eyeball.