Convex vs. Concave Lens: 7 Differences, Definition, Pros & Cons

A lens is a transparent, curved piece of glass or plastic that bends and focuses light in a certain way. How much and in which direction light bends depends on how curved the object is.

Glasses, microscopes, and telescopes all have them. Based on how it looks, the lens is said to be convex or concave. The first one makes the parallel beams of light come together, while the second one spreads them out.

So, the point of focus for a convex lens is where all the light rays meet, which is called the “point of convergence.” For a concave lens, the point of focus is where the light rays appear to split apart, which is called the “point of divergence.”

Let’s look at the picture below to see how convex and concave lenses are different.

What are Convex Lens?

Convex lenses feel bigger in the middle than they do on the edges. The lens is curved outward, and when light beams pass through it, it bends them and brings them closer together.

This is why it is also called a converging lens. Check out the picture below:

So, the point where the light rays meet is called the focal point or main focus, and the distance between the centre of the lens and the main focus is called the focal length.

It also makes a true and upside-down image, but if the object is too close to the lens, it can also make a virtual image.

Convex vs. Concave Lens

These lenses are used to make an object look clearer and bigger by focusing a beam of light on it.

A camera’s lenses are convex so that light beams can focus on the person or thing being photographed.

What are Concave Lens?

Concave lenses are those where the middle is narrower than the edges. A diverging lens has the shape of a concave lens, which is round on the inside and bends the beams outward.

This makes the light rays that hit it go in different directions. This also makes the thing look smaller and farther away than it really is. The resulting image is virtual, shrunken, and upright.

From what you can see in the picture, it looks like the light rays are spreading out from a virtual point called the principal focus or focal point. Also, focal length is the distance between the point where you want to focus and the centre of the lens.

Side mirrors on cars and motorcycles, for example, have concave lenses. They can also be used in movie projectors to spread the image.

Convex vs. Concave Lens

Comparison Chart: Convex and Concave Lens

ComponentsConvexConcave
DescriptionThe convex lens makes the objects look larger and bigger due to the thicker center.The concave lens makes the object smaller and shorter due to the thinner center.
StructureA convex lens is thicker at the center and thinner at the edgesA concave lens is thinner at the center while thicker at the edges
Light RaysThe convex lens bends the light rays toward each otherConcave lens spreads the light rays and cannot form an image on the screen
Focal LengthA convex lens has a positive focal length and is also known as a positive lens.A concave lens has a negative focal length and is also known as a negative lens.
Image FormationAn only virtual image can be formed through a convex lens due to the bending of light rays.The concave lens forms both virtual and real images due to the spreading of the parallel rays.
Parallel RaysConvex lens converge the parallel rays and also called converging lensConcave lens diverges the parallel rays and is also called the diverging lens
UsageA convex lens is used to correct the hypermetropia or long-sightednessA concave lens is used to correct myopia or short-sightedness

Key Difference Convex and Concave Lens

When it comes to the difference between convex and concave lenses, it’s important to remember the following:

  • The light rays that pass through a convex lens come together at a certain point. A lens with a concave shape spreads out the light rays that hit it.
  • The curve on a convex lens goes outward, while the curve on a concave lens goes inward.
  • When light passes through a convex lens, the light rays come together and focus on a single point. On the other hand, light rays spread out as they go through the concave lens.
  • The structure of a convex lens is thicker in the middle and thinner at the edges. On the other hand, concave lenses have a shape that is thinner in the middle and thicker at the edges.
  • A convex lens has a focal length that is greater than zero, while a concave lens has a focal length that is less than zero.
  • A convex lens produces a real image most of the time, but when the object is in the centre of the focus and optical center, it can also produce a virtual image.On the other hand, the image made by the concave lens is right-side up, virtual, and smaller than the thing.
  • The thicker centre of convex lenses makes things look bigger and closer. On the other hand, concave lenses have a thin centre that makes the object look far away and small.
  • A convex lens is used to treat hyperopia, or farsightedness. On the other hand, the concave lens can help people who are nearsighted or farsighted.

Convex Lens & Concave Lens Examples

Convex Lens Examples

Convex lenses can be found in the eye, eyeglasses, microscopes, projectors, cameras, telescopes, and projectors.

Concave Lens Examples

Concave lenses are used in binoculars, telescopes, glasses that correct nearsightedness, flashlights, and CD and DVD players that look like lasers.

Convex vs. Concave Lens Similarities

  • Both convex and concave lenses are made of glass or something else that is clear.
  • Both lenses have at least one surface that is curved.
  • The surface of both flat and curved lenses is smooth.

Convex vs. Concave Pros and Cons

Pros and Cons of a Convex Lens

Pros of a Convex Lens

  • Using a convex lens to magnify something makes it look bigger and bigger.
  • Convex lenses are also used to focus the image in cameras, but by moving the lens, you can change the size of the image.
  • Peepholes are small, security-related holes in the front door. The convex glass in these peepholes allows you to see clearly who is outside.

Cons of a Convex Lens

  • When used to magnify in binoculars and telescopes, convex lenses may not move light as well as they should, which can cause blurring and distortion.
  • The bright objects in an image look like they have fringes because the convex lens of the camera bends different colours of light.

Pros and cons of a Concave Lens

Pros of a Concave Lens

  • The flashlight’s concave lens can make the light source brighter and give off a wider beam.
  • Photographers used both concave and convex lenses in their cameras to improve the quality of the pictures they took.

Cons of a Concave Lens

  • Because the middle of a concave lens is thinner, it can make things look smaller and shorter.
  • A concave lens can produce both inverted and true images. Depending on where the object is in relation to the lens, it can either enlarge or shrink the image.

Convex vs. Concave Lens

FAQs

Is a Converging Lens Concave or Convex?

A convex lens is called a converging lens because it brings all the light rays to one point.

What Are Convex Lenses Used For?

Glasses with convex lenses are used to correct farsightedness. It is used in everything from cameras to microscopes to magnifying glasses.

Which Lens Is Used in the Telescope?

In a telescope, a convex glass lens is used to bend the light and make it more clear.

What Is the Difference Between Concave and Convex Mirrors?

A concave mirror is a spherical mirror with a curve that goes inward. A convex mirror, on the other hand, has a curve that goes outward.

Conclusion

With the above examples and pictures, you should have a good idea of how the two types of lenses are different. Convex and concave lenses are often used together to make images that are sharper, clearer, and better.

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