A lens is defined as a curved, transparent piece of glass or plastic that focuses and refracts light rays in a specific way. The curvature of the object determines how far light is bent and in which direction it is bent. They are commonly found in spectacles, microscopes, and telescopes. The lens is classified as convex or concave based on its shape. The former brings the parallel beam of light together, while the latter disperses it. So, in the case of a convex lens, the point of focus is the point where all the light rays meet, i.e. point of convergence, whereas in the case of a concave lens, the focal point is the point from which the light rays appear to diverge, i.e. point of divergence. In this article, we will have a closer look to these types of lens and the difference between concave and convex lens.
What is a lens?
A lens is an optical tool that converges and diverges a light beam through refraction. It is an optical trans-missive system that uses refraction to focus or spread a light beam. A single lens is made from a single piece of transparent material. The composite lens is made up of several simple lenses that are normally aligned along a common axis. Based on the shape, there are two types of lens:
- Concave lens
- Convex lens
A convex lens (also known as a positive lens) has glass or plastic surfaces that bulge outwards at the center. A convex lens is also known as a converging lens because the parallel light rays passing through it curve inward and touch (converge) at the focal point, which is located just beyond the lens. A convergent lens is another name for a convex lens. There are three types of convex lens.
- Plano-convex lens
- Concavo-convex lens
- Bi-convex lens
A convex lens is used for a variety of purposes such as glass enlargement, mirrors, telescopes, hypermetropia correction, and so on.
A concave lens has external surfaces that curve inside, causing parallel light rays to curve outwardly or diverge. As a result, concentric lenses are also known as divergent lenses. When considering the concave lens internally, the difference between concave and convex lens becomes clear. A concave lens diverges the straight light beam coming from the source to create a reduced, upright, or digital image. Depending on the light source, it can generate both real and virtual objects. There are three types of concave lens:
- Bi-concave lens
- Plano concave lens
- Convexo concave
Difference between concave and convex lens
A convex lens, also known as a converging lens, focuses light rays to a specific point, whereas a concave lens, also known as a diverging lens, diverges light rays. Concave and convex lenses are frequently used together to form the Concave – Convex lens. When these lenses are combined, sharper images are produced. The majority of eyeglass lenses are made up of a combination of convex and concave lenses. Cameras, telescopes, and microscopes all use lenses to help us see the world more clearly. Below points tell us the difference between concave and convex lens.
|A concave lens is thinner in the center and thicker around the edges.||A convex lens has a thicker center and a thinner edge.|
|It is also known as Diverging Lens.||It is also known as Converging Lens.|
|Used in glasses, some telescopes, and spy holes in doors, among other things. It is also used to correct short-term vision problems.||Used in cameras, overhead projectors, projector microscopes, simple telescopes, magnifying glasses, and other devices. It is also used to correct long-term vision problems.|
|Negative Focal Length||Positive Focal Length|
|It diverges the incident rays away from the principal axis.||It converges the incident rays towards the principal axis.|
|The image formed is an upright, virtual, and smaller size than the object. The position of the image formed is in between the lens and the object regardless of the object’s position||The image formed is inverted, real and smaller than the object when the object is placed at focus. The image formed is the inverted, real, and the same size as the object when the object is placed at 2F. The image formed is inverted, real and larger than the object when the object is placed between 2F and F. No image is formed when the object is placed at focus (F). The image formed is upright, virtual, and larger than the object when the object is placed on the same side of the lens.|
|Virtual, erect and diminished image||Real and inverted image.|
Nearsightedness correction eyeglasses use concave lenses. Nearsighted people have difficulty seeing distant objects because the distance between the eye’s lens and retina is greater than it should be. Concave lenses placed in front of a nearsighted eye reduce light refraction and increase focal length, allowing an image to form on the retina. Convex lenses are used in eyeglasses to correct farsightedness, which occurs when the distance between the lens of the eye and the retina is too close, causing the focal point to be behind the retina. Convex lenses increase refraction while decreasing focal length.