Parallel rays of light incident on a concave lens are refracted in such a way that they appear to diverge from a point on the principal axis. This virtual point is also called the principal focus, but in this case, ...

Parallel rays of light incident on a convex lens are refracted and converge to a point on the principal axis. This point is known as the principal focus of the lens.

The principal focus of a lens is the point on the principal axis where parallel rays of light, after passing through the lens, converge or appear to diverge from. For a convex lens, these rays converge to a point, while ...

The paper burns because the parallel rays of sunlight are converged by the lens to form a sharp and bright spot on the paper. This spot acts as a real image of the Sun, concentrating sunlight at that point and ...

Lenses with small apertures and where the two centres of curvature are equidistant from the optical centre are referred to as thin lenses. The discussion in this chapter is specifically limited to the behavior of such thin lenses.

The principal axis of a lens is an imaginary straight line passing through the two centres of curvature (C1 and C2). It is a key reference line used to describe the geometry and behavior of the lens.

The optical centre of a lens, represented by the letter O, is the central point of the lens. A ray of light passing through the optical centre does not undergo any deviation. It is a crucial point for understanding the ...

The aperture of a lens is the effective diameter of its circular outline. In this chapter, we focus on lenses with small apertures, where the aperture is much less than the radius of curvature, and the two centres of curvature ...