What is the point?

Focal point refers to the convergence point of parallel rays after refraction by lens or reflection by curved mirror.

In optics, focus plays a vital role. When parallel beams pass through a convex lens, they will intersect at a point on the other side of the lens, which is called the focus. Similarly, for concave mirror, when light is reflected, it will also converge to a specific focus. The existence of focal point enables optical devices to realize imaging and focusing functions, which are the basic elements in the design and application of optical systems.

In addition, in photography, the focus is often used to describe the point or area where the lens is aimed at the clearest image, which is very important for taking clear and layered photos.