Convex Lens

A lens is a transparent object that has two opposite surfaces, with at least one curved surface, which has the ability to focus light.

There are a variety of types of lenses. Lenses differ from one another in terms of their shape and the materials from which they are made

Generally lenses can be classified into two types:

  • The convex lens, also called a converging lens
  • The concave lens, also called a diverging lens

Let's know more about convex lens.

You might know magnifying glass is being used to ignite a piece of paper.

To understand how the magnifying glass has ignited the paper, let's take a closer look at the lens used in the magnifying glass.

Anatomy of a Convex Lens

A lens is merely a carefully ground or molded piece of transparent material that refracts light rays in such as way as to form an image. The lens used in the magnifying glass is thicker in the middle and thinner at the ends.

This type of lens is called a convex lens.

When a convex lens is sliced into several pieces, you see that it has a series of small prisms, stacked one over the other, together with a small glass slab, at the centre. The prisms are stacked in such a way that the prisms in the upper half have their base downwards and the prisms in the lower half have their bases upwards. Due to this arrangement, the lens bulges in the middle and is thinner at the ends.

Refraction by a Convex Lens:

On allowing light rays to pass through the convex lens, you will see that when a ray of light passes through the top prism, after refraction, it bends downwards towards the base of the prism.

When a ray of light passes through the second prism, it also bends towards the base of the second prism.

But, when a ray of light passes through the small glass slab, at an angle of 90°, it emerges from the glass slab in a straight line, without bending. Similarly, when a ray of light passes through the lower set of prisms, it bends in an upward direction, towards the base of the prisms.

When light rays pass through all the parts of the convex lens, they bend or are refracted in such a way that all the refracted light rays meet or converge at one point. This point is called the focus and is marked as F.

A convex lens is also known as a converging lens, because the light rays, after passing through the lens, converge or meet at one point. In the paper burning experiment, the rays from the sun get refracted after passing through the convex lens in the magnifying glass, and converge on the piece of paper, producing a real image of the sun. The converging rays concentrate the solar energy on the paper, causing it to get ignited.