Difference Between Concave and Convex Lens

A lens enables us to see things around us, to see different colours, and to make differences between various objects. Our eyes have a crystalline lens through which we see the world.

This lens is transparent. This lens has a biconvex structure, and along with the cornea, it refracts light rays to be focused on the retina. 

Lens both refract as well as a focus light.

The lens curve makes the whole difference as its shape determines in which direction and to what extent the light will bend. A lens can be defined as a concave or convex lens based on its shape.

The convex lens also is known as a converging lens as it converges the light to form an image on the other side.

Key Takeaways

1. A concave lens is a lens that is thinner in the middle than at the edges and causes light rays to diverge.
2. A Convex lens is a lens that is thicker in the middle than at the edges and causes light rays to converge.
3. A concave lens is used for correcting nearsightedness, while a convex lens is used for correcting farsightedness.

Concave vs Convex Lens

Convex lenses are commonly used in corrective lenses for glasses and contact lenses. They are also used in cameras and telescopes to magnify images. Concave lenses are used in some types of eyeglasses to correct nearsightedness and in some types of cameras to create wide-angle shots.

A convex lens is a lens through which light rays pass when contact. Objects appear smaller and far in a concave lens, whereas objects appear more prominent and significant in a convex lens.

Comparison Table

Parameter of Comparison	Concave Lens	Convex Lens
Definition	It is a diverging lens that spreads out the light.	It is a converging lens which converges the refracted rays.
Curve	The curve is outward in it.	The curve is inward in it.
Image and Objects	The image formed is accurate, and the object appears closer and more significant.	The image formed is virtual, and the object appears smaller and far away.
Focal Length	The focal length is positive.	The focal length is negative.
Usage	Used to correct the problem of short-sightedness or myopia.	Used to correct the problem of farsightedness or hypermetropia.

What is Concave Lens?

Curiosity is the mother of invention. Every scientific experiment starts with a zeal to discover something new, and we can assume that the same interest brings the idea of the lens, their types, and, most importantly, their uses.

Objects could be perceived with different images and applied in many cases. A concave lens has a thinner centre and thicker edges. Its surface is inwardly curved. It spreads the light rays falling on its surface, which is why it is also called a diverging lens.

There is a specific point where the light rays converge after getting reflected. This point is known as the principal focus of the concave lens.

At this point, the parallel light moving to the axis of the lens is focused.

The images formed by the concave lens are always virtual, upright, and smaller than the object. The size of the virtual images increases because the distance between the lens and the object decreases.

Concave lenses are used in eyeglasses, telescopes, flashlights, side mirrors of cars and motorbikes, movie projectors, etc.

What is Convex Lens?

The curiosity for the convex lens is more attractive as it can be used to start a fire with the help of the sun. Many children must have tried this exciting lens game after studying Physics.

A convex lens is relatively thicker at the centre but thin at the edges, and these edges are curved outward rather than inward.

A convex lens has the property of converting the beams of light rays, which are initially parallel to the principal axis, to a point called the focus on the other side of the lens.

A convex lens can produce a virtual or real image according to the object’s position. The image produced will be virtual and erect if the purpose is located at a distance smaller than its focal length.

Whereas, if the object is lying at a distance equal to its focal length or greater than the focal length, then the image produced will be accurate and inverted. 

It is used to correct hypermetropia, i.e., long-sightedness in which a person cannot see nearby objects. It is also used to make optical instruments like microscopes, telescopes, magnifying glasses, etc.

Being converging in nature, it is used in the camera lens to focus light on a clear picture. Even the lens in human eyes is also convex, which can change its focal length according to the object’s position and forms its image at the retina.

Main Differences Between Concave and Convex Lens

1. The most straightforward difference between a concave and a convex lens is its physical appearance. A Convex is thin at the edges and thick at the centre, while a concave lens is thin at the centre but thick at its edges.
2. The curvature of a convex lens is outward-facing, whereas the curvature in a concave lens is inward-facing.
3. The focal length of a convex lens is positive, while the concave lens has a negative focal length.
4. A convex lens has a converging nature as it merges the light passing through it and focuses them at a particular point. On the other hand, a concave lens has diverging nature as it diverges the light rays passing through it, i.e., it spreads the light rays. 
5. A convex lens can form a virtual and actual image of the object according to its distance from the lens, whereas the concave lens forms only a virtual image of the object.
6. A convex lens is used to correct hypermetropia, i.e., long-sightedness, while a concave lens corrects myopia, i.e., short-sightedness. 

References

1. https://www.universetoday.com/82338/concave-lens/
2. https://www.universetoday.com/82589/convex-lens/