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Uses of Concave Lens

Last updated date: 09th Apr 2024
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What are Lenses?

A human is a natural optical lens that helps us see real-life objects with exact color distinctions. 

However, a few people lose the ability to see far/near objects, for them, a concave/convex lens (resp.) works as a helping source to fulfill their clear vision dreams.

A concave lens is a diverging lens that helps people view objects at large distances if they are dealing with Myopia; however, for people dealing with hypermetropia, a converging lens, convex lens is used, which we will discuss in this article.

We will also discuss the application of concave lenses with the uses of a concave and convex lens.

Concave Lens

A concave lens is one that is thicker at the edges and thinner in the centre. This type of lens bends light rays outwards. A concave lens is also known as a diverging lens as it diverges the light rays. It is made up of a number of prisms, with the base of each prism pointing away from the lens's centre. The lens's central section is a simple parallel-sided glass.

Light rays can pass through the parallel-sided glass slab without deviating.

The upper portion of the lens deviates light rays upwards, while the lower portion deviates light rays downwards. These lenses are used in those types of glasses that are known to correct the defects of vision i.e., myopia and hypermetropia. Materials used to make these lenses can either be glass or plastic, which are then polished and eventually moulded into different shapes. In contrast to a prism, which refracts light without focusing, a lens can focus light to form an image. 

Types of Concave Lens

The following are the different types of concave lenses:

  1. Double concave

  2. Plano concave

  3. Convexo-concave

The Formula of Concave Lens

To know which type of image is created by a concave lens, the lens formula of that concave lens is used. It is also used to identify the position of the image. The formula for the concave lens is as follows:

1/f=1/v +1/u


'f' = the focal length 

'v' = distance of the image. 

'u' = distance of the object. 

Uses of Concave Lens

  1. In a Telescope

Concave lenses are magnifiers found in telescopes and binoculars. The object is magnified by the concave lenses. Concave lenses are used before or in the eyepiece of telescopes and binoculars to help people focus more clearly.

  1. Applied to Glasses

Concave lenses are used to correct myopia, also known as nearsightedness. Concave lenses in spectacles are used to compensate for the shortage by spreading light rays out before they reach the eyeball. This improves the person's ability to see items in the distance.

  1. In use in Peepholes

Peepholes are security devices that provide a 360-degree view of objects or areas outside of walls or doors. They are also known as door viewers. A concave lens is used to reduce the proportions of an object while providing a wider view of the object or area.

Concave and Convex Lens

We find the application of concave lens in treating vision issues and for that, we find the uses of a concave lens in daily life; let’s understand how:

A concave lens is used to treat myopia because the lens diverges the parallel light rays coming from distant objects. Therefore, a virtual image forms at a distant point of the myopic eye. 

Now, that the light rays are at the proper distance, the objects can be easily focused onto the lens, and a clear image is thus formed on the retina.

Below is the diagram to illustrate one of the concave lens examples on myopic eye-correctness (nearsightedness):

(Image will be uploaded soon)

Convex Lens

A person who can view far objects clearly, but when it comes to viewing nearby objects, he/she fails to get a clear vision; let us understand what is the use of convex lenses here?

If a person is hypermetropic, the image of a nearby object forms behind the retina. This means that light is focused too far back in the eye that causes things that are close up to appear blurred.

At this moment, a convex lens works as a gold mine for people dealing with farsightedness. 

When a ray of light comes from the distant source is reaching the retina, before it reaches, the convex lens converges and works as a pathway for these rays to converge on the retina.

Below is the diagram to illustrate one of the convex lenses examples:

(Image will be uploaded soon)

Now, let’s understand what are the uses of a concave lens followed by a convex lens, and also understand the 5 uses of concave and convex lenses.

Uses of Concave and Convex Lens

So, we will first start with the uses of concave lens Class 10:

We find many uses of a concave lens in daily life, the first two uses of the concave lens are:

  • We Find the Use of Concave Lenses in Car Headlights.

A concave lens works as a safety factor for driving at night. This lens diverges the light to far distances that help in a clear view of the far vehicles at night.

  • Concave Lenses Are Used in Peepholes.

We find a small lens fixed in the middle of our doors to view who ranged our doorbell, yes, these are the peepholes to peep who is outside the door. Here, the concave lens gives us a panoramic view of the person standing just opposite the door.

The Rest Three Uses of Concave Lens are:

  • Concave Lens in Lasers

Various devices like scanners, medical equipment, and CD and DVD players use laser beams. Since laser beams are highly-focused and we use small concave lenses to widen the laser beam to sharply access a specific area.

  • Concave Lenses in Glasses.

(About it, we have discussed in the above text on nearsightedness).

  • In Flashlights or Torch

Uses of Convex Lenses

  • Magnifying Glass

When the rays enter the convex lens of the magnifying glass, these rays focus on a specific focal point at the center of it.

  • Eyeglasses

(About this, we discussed in the above text on farsightedness).

  • In Cameras

Most of the cameras that we use have convex lenses, while a few have concave lenses.

Convex lenses help focus on the image well and magnify these at the same time.

  • Microscope Lenses

Convex lenses are also called microscopic lenses. 

A simple microscope usually has three lenses, out of which, one (convex lens) produces an inverted and magnified image of microorganisms like bacteria, amoeba, etc.

  • Multi-Junction Star Cells

Convex lenses are widely used for multi-junction electric cell. The lens is added above the Fresnel lens to increase the output power of the setup and retrieve the requirement for the employment of solar trackers. 

Interesting Fact

In cameras, we find the uses of a concave and convex lens to get clear images in photography.

To ameliorate the quality of photographs, camera manufacturers use combinations of convex and concave lenses. Here, a convex lens is used as the primary lens of a camera that causes distortions in the photos, which is called chromatic aberrations. Combining both concave and convex lenses eliminates these undesirable effects.

FAQs on Uses of Concave Lens

1. What is the difference between a convex lens and a concave lens?

Convex lenses are frequently given all of the credit. They are the most common type of lens used in photography and other common applications, and they are responsible for magnification. Convex lenses have a thicker centre and taper outwards. 

Concave lenses, on the other hand, have a central inward curve that makes the edges appear thicker. A convex lens is used to magnify and enlarge the size of the image formed

2. On what principle does concave lens work?

After passing through the concave lens, all light rays diverge and appear to meet at a point on the lens's principal axis when produced backward. This is referred to as the principal focus of a concave lens. As a result, refracted rays appear to diverge from the focal point. Concave lenses are the inverse of convex lenses. After passing through it, the parallel beam of light rays diverges. A concave lens has two foci as well

3. What happens when light shines through a concave lens?

After passing through the concave lens, all light rays diverge and appear to meet at a point on the lens principal axis when produced backward. This is referred to as the principal focus of a concave lens. As a result, refracted rays appear to diverge from the focal point. Concave lenses are the inverse of convex lenses. 

4. What type of lens is used in flashlights and torches?

The flashlight lens is a concave lens that is put in the path of the light beam and diverges the rays so that the beam of light is distributed over a vast surface in darkness and one can see objects clearly even in darkness. This now means that the diameter of the beam has increased as it can now cover a large area and due to this visibility of the item becomes better as well. The image formed is virtual, erect, and enlarged.

5. Name the sort of mirror that is used in the following situations: 

(a) a car's headlights

(b) a car's side/rear-view mirror

(c) A solar-powered furnace.

Provide evidence to back up your claim.

(a) Car headlights with a concave mirror for a parallel light beam following reflection from the concave mirror.

(b) Convex vehicle side/rear-view mirror, which generates a virtual erect and decreased image to provide a broader visual field.

(c) Solar furnace: A concave mirror is used to concentrate sunlight in order to generate heat in a solar furnace.

6. What is the focal length of a lens?

In a nutshell,  the focal length of the lens is the measure of how “zoomed in/enlarged” your lens is. 

Much like viewing objects through binoculars, you may be at 35 mm and are able to see the entire Himalayas. If you zoom in to 400 mm, you can only see one tree on the mountain. The focal length measurement helps the photographer understand what the angle of view will be.

So, for calculating the focal length of a lens, one must know the distance from an object to the lens and the distance from the lens to the image. The focal point is the specified point at which parallel light rays meet.

7. What is the power of a lens?

Power is the ability of the lens to bend the light falling on it.

A point to note that is, a lens of shorter focal length bends the light rays more because it has more power.

A convex lens is a converging lens so it converges the light rays towards the principal axis. 

Here, we have a brief explanation of the relationship between the focal length and the power:

A focal length is the reverse of the power. The equation for the same is given as;

                              f (focal length in m) = 1/P (power in dioptre)

The S.I. unit of power of a lens is 1/m a.k.a diopter.

The focal length (f) of a converging lens is always positive, so the power of a converging lens is also positive.

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