ABSTRACT
A lens consists of a finite width of a transparent medium bound by two surfaces, both spherically shaped, or one plane with the other spherical. They form images based on the property of refraction. Lenses are classified as thick or thin depending on the width of the refracting medium between the two surfaces relative to the diameter of the lens. For a thick lens, analyzing the optics of light rays incident on it requires that the laws of refraction be applied for the two surfaces independently. However, thin lenses are a special case of thick lenses, and formulation of a thin lens reduces to a simple one in treating it as one entity. Except for limited cases that need clarity, light waves are dealt with as rays that follow straight line propagation. This chapter will show that in any optics problem where lenses are used, light rays emitted by an object and incident on a lens get refracted, converging or diverging, forming an image.
