Biconvex Lens

Biconvex lens

Biconvex Lenses- Definition and Meaning

Biconvex lens are the simple lenses which comprises of two convex surfaces in spherical form, generally having the same kind of radius of curvature. These are also called as convex-convex lens.

A Biconvex lens is as shown in the figure below-

Biconvex Lens

Being a kind of simple lens, the biconvex lens has wide range of applications of it, but it is not limited to, control and focusing of laser beams, quality imaging and also the other kinds of optical instruments.

In a biconvex lens or a Plano-convex lens, a collimated or accurately parallel beam of light passes through the lens and converges at a spot or focus coming behind the lens. In such case, this lens is known as a converging or positive lens. The distance coming from the lens up to the spot is called as the focal length of lens. Since there is a curvature on both the sides of lens, there will be around two focal points and also two centers. The line that is drawn through middle of the biconvex lens is known as the principal axis. This is as shown in the figure below-

Biconvex Lens

A human eye lens is an best example of an Biconvex lens. For an eye, in order to see the objects at hand, the light rays coming from the objects has to bend more sharply in order to bring them on to the focus of retina; the light rays coming from a distant object requires more less refraction. To acquire this, it has to be of highly elastic form so that that the shape can be altered and thus can be made less or more convex. The higher convex a lens, greater is the refraction.

Biconvex Lenses- Properties

Some of the characteristic properties of a biconvex lens are given below-

  • Biconvex lens are said to possess positive focal length
  • They are said to have shorter focal lengths
  • They have the ability to converge the incident light
  • They have the capability of forming both the real as well as the virtual images
  • They minimize the spherical aberration and can also cancel the coma and the distortion with a conjugate ratio corresponding to unity.

The Biconvex lenses are known to be symmetrical in form, having equal radii on both the sides. They are usually recommended for the purpose of virtual imaging incase of real objects, and also for a positive conjugate ratios ranging between 0.2 – 5.

Biconvex Lenses- Uses & Applications

These lenses has around a number of uses of which some of them are listed below-

  1. Biconvex lens are used as a magnifying or condensing lenses.
  2. They are also used as objectives or magnifiers
  3. These are utilized in many of imaging systems such as the telescopes, monocular, microscopes, binoculars, cameras, projectors, etc.
  4. These are used in producing the virtual image in case of a human eye and a real image in case of the photographic films or an optical sensor
  5. These lenses are also used as a burning-glass.
  6. These are used in the applications of image relays and also in various kinds of industries

Hence a biconvex lens is one of the best lenses that can be used in a condition where a beam of light incident on lens is diverging in nature and also the beam that leaves the lenses converges symmetrically.

Practise This Question

Two electric charges 12 μC and 6 μC are placed 20 cm apart in air. There will be a point P on the line joining these charges and outside the region between them, at which the electric potential is zero. The distance of P from 6 μC charge is