A lens that is thicker at the centre and thinner at the edges is known as convex lens.
An optical lens is generally made up of two spherical surfaces. If those surfaces are bent outwards or convex, the lens is called a biconvex lens or simply convex lens. These lenses can converge a beam of light coming from outside and focus it to a point on the other side. This point is known as the focus and the distance between the centre of the lens to the focus is called the focal length of convex lens. However, if one of the surfaces is flat and the other convex, then it is called a plano-convex lens.
Difference between convex and concave lens:
Apart from the convex lens, there is another type of lens known as concave lens. The major differences between the two are:
- Convex lens converges a straight beam of light while concave lens diverges it.
- A convex lens is thicker at the centre and gets thinner as it moves towards the image, whereas, a concave lens is thinner at the centre with increasing area as it moves towards the edges.
- A concave lens will always produce diminished, upright and virtual image of the object in front of it. But the nature of the image produced by a these lens depends upon the position of the object. It can form both real and virtual images depending on where the light is coming from.
Uses of convex lens
These are used for a variety of purposes in our day to day lives. For example,
- The lens in the human eyes is a biconvex lens. So the most common use of the lens is that it helps us to see.
- Another common example of the use convex lens is a magnifying glass. When an object is placed in front of it at a distance shorter than the focal length of the lens, it produces a magnified and erect image of the object on the same side as the object itself.
- It is used to correct Hypermetropia or long-sightedness.
- It is used in cameras because it focuses light and produces a clear and crisp image.
- It is also used in other magnifying devices such as microscopes and telescopes.
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