What is the focus in optics?

The focus in optics refers to the point where light rays converge. This convergence occurs when parallel light rays, upon passing through a lens or reflecting off a mirror, meet at a specific point. This point is crucial for forming clear images, as it is where light rays from an object come together after passing through the optical system, allowing the system to produce a clear image of that object on a sensor or a surface.

In imaging systems, such as cameras or the human eye, the focus is essential for achieving clarity and sharpness. If light rays do not converge properly, the image will appear out of focus or blurred. This is why identifying the actual point of convergence is fundamental to understanding how optical systems work.

Other options touch on various aspects of optics, but they do not correctly define the focus. For instance, the notion of light rays diverging or images becoming blurred relates to other optical phenomena, while the reference to points under visible light doesn’t encapsulate the precise definition of focus in optical systems.