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Spherical Lenses and Image formation

The topic explains the formation of images by Lenses: Concave lens and Convex lens. We will also find out the lens formula of different lenses.

  • A lens is bound by at least one spherical surface. In such lenses, the other surface would be planes (plano-convex lens and plano-concave lens).
  • Convex lens: It has two spherical surfaces that bulge outwards.
    • It is thicker in the middle as compared to the edges
    • It converges light rays, and it’s called converging lenses
  • Concave lens: It has two spherical surfaces that curve inwards.
    • It is thicker at the edges than at the middle
    • It diverges light rays and hence is also called diverging lenses

Image Formation

The image will be realistic, reversed, and magnified. When an object is put inside F on a convex lens, the image will be virtual, upright, and magnified, and it will be on the same side of the lens as the object. All rays diverge when a lens is concave. Virtual pictures are created using concave lenses.

 

(a) Converging action of a convex lens, (b) diverging action of a concave lens : Unacademy
(a) Converging action of a convex lens, (b) diverging action of a concave lens

Image Formation through Lenses

As any observer views the picture of the item via the lens, images are produced at the spots where they are seeing. As a result, if the passage of numerous light beams via a lens is tracked, the light rays will intersect at a point as the lens refracts them.

Nature : Unacademy

Image formation by a Convex lens:

Table: Nature, position and relative size of the image formed by a convex lens

Nature-2 : Unacademy

Lens Formula: 

The formula for spherical lenses is given by:

1/v – 1/u = 1/f

This formula describes the relationship between object distance (u), image distance (v), and the focal length (f).

Power of a Lens:

 It is the ability of a lens to converge or diverge light rays. It is the reciprocal of its focal length.

  • The SI unit of power of a lens is dioptre
  • The power of a convex lens is positive, and that of a concave lens is negative