Concave and Convex Lenses - Definition, Image Formation, Uses, FAQs

Edited By Vishal kumar | Updated on Sep 24, 2024 11:16 AM IST

The word "lens" comes from the Latin word "lentil," which refers to the little beans that have been a staple of Mediterranean cuisine since ancient times. Because of the convex shape of lentils, their Latin name was coined for glass with a similar shape.
Lenses are used to focus or scatter light due to the way they refract light that strikes them. The composition, size, thickness, curvature, and combination of lenses employed can vary the amount of light that enters the lens in a variety of ways. Lenses are made for a variety of applications, including cameras, telescopes, microscopes, and spectacles. Other more contemporary gadgets that take advantage of lenses' capacity to diffuse or condense light include copying machines, image scanners, optical fiber transponders, and cutting-edge semiconductor fabrication equipment.

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Image Formation with concave lenses
Concave lenses
Difference between Concave and convex lenses.
Uses of Concave Lens:

Concave and Convex Lenses - Definition, Image Formation, Uses, FAQs

A lens is an optical instrument that, using the concept of refraction, either converges or diverges the light beam that strikes its surface. The converging or diverging of light beams is accomplished using a piece of glass with the proper form. It is shaped so that light rays refract to generate an image.

The lens' power is measured by the amount of convergence or divergence it imparts to the light beams that pass through it.

When these lenses are used together, the result is a sharper image. Concave lenses are used in most eyeglass lenses. Different lenses are used in cameras, telescopes, and microscopes to let humans see the world more clearly.

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Image Formation with concave lenses

To create spherical lenses, two spherical transparent surfaces are combined. Spherical lenses can be divided into two categories. Convex lenses are made by joining two spherical surfaces that bulge outward, and concave lenses are made by joining two spherical surfaces that bend inward. The difference between concave lenses is one of the most important. Because the rays converge after passing through convex lenses, they are also known as converging lenses, whereas concave lenses are known as diverging lenses because the rays diverge after passing through them.

Rays falling on concave lenses should follow these guidelines.

1. When a beam obliquely strikes a concave or convex lens image at their pole, it continues on its path.

2. When a ray strikes concave or convex lenses parallel to the principal axis, the reflected ray travels through a focus on the principal axis.

3. When a ray passes through focus and collides with concave or convex lenses, the reflected ray passes parallel to the principal axis.

convex (converging)lens convex lens ray

convex lens ray diagram with image formation by convex lens image

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concave (diverging)lens concave lens ray

concave lens ray diagram with image formation by concave lens image

Convex Lenses for Image Formation:

Concave lenses

1. A virtual image is produced at the focus when an object is positioned at infinity. The image is a fraction of the size of the real thing.

2. A virtual image is produced between the pole and the focus of the convex lens when an object is positioned at a finite distance from the lens. The image obtained will be significantly larger than the object.

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Difference between Concave and convex lenses.

Properties	Concave lens	Convex lens
Look	The middle of a concave lens is thinner, while the edges are thicker.	The middle of a convex lens is thicker than the edges, while the margins are thinner.
Also known as	Diverging lenses	Converging lenses
Focal length	Negative	Positive
Incident rays	The incident rays are diverged away from the main axis.	The incident rays converge towards the primary axis.
Applications	Used in glasses, some telescopes, and door spy holes, among other things. It's also utilized to remedy a problem with short-sightedness.	Used in cameras, overhead projectors, projector microscopes, basic telescopes, magnifying glasses, and other devices. It can also be used to correct a long-sightedness condition.

NCERT Physics Notes :

Uses of Concave Lens:

Concave lens used in glasses. Concave lenses are most commonly used to correct myopia, which is also called near-sightedness.

Uses of concave lenses in lasers.
Use of concave lenses in cameras.
Used in flashlights.
Concave lens used in peepholes.

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Frequently Asked Questions (FAQs)

1. What are the purposes of concave lenses?

Diverging lenses (concave) are used to shift the focus of your eye lens backwards so that it can focus on the retina if you have myopia or nearsightedness. In the case of hypermetropia (farsightedness), a converging (convex) lens would be used to bring the focus closer.

2. What happens when you put a pair of lenses together?

A lens combination. When two lenses are combined, the first creates an image that is then used as the subject of the second lens. The magnification of a combination is the ratio of the resulting image's height to the object's height.

3. How can you tell whether a lens is convex or concave?

The middle of a concave lens is thinner than the edges, while the edges are thicker. A convex lens has a thicker center and thinner margins. Used in cameras, overhead projectors, projector microscopes, basic telescopes, and magnifying glasses, among other things.

4. Is it true that a concave lens magnifies or distorts objects?

Objects appear larger and further away when viewed via a convex lens. A concave lens distorts the perspective of objects, making them appear smaller and closer.