What is the effect called when light rays coming together focus at a single point?

The effect when light rays come together and focus at a single point is called convergence. This phenomenon occurs when parallel light rays, after passing through a lens or being reflected off a curved mirror, come together at a focal point. Convergence is important in optics as it is a key principle in lens design, particularly for corrective lenses used in eyeglasses.

Understanding convergence is essential because it helps opticians determine how lenses will affect the path of light entering the eye, which in turn influences how clearly a person can see. In practical applications, converging lenses (convex lenses) are used to correct hyperopia (farsightedness) by converging light rays before they enter the eye, allowing for proper focus on the retina.

This concept is distinct from divergence, which refers to light rays spreading apart, and from refraction or reflection, which describe the bending and bouncing of light, respectively.