Which property allows lenses to focus light?

Lenses focus light primarily due to the property of refraction. When light passes from one medium to another, such as from air into glass or plastic, its speed changes, causing the light to bend. This bending effect enables lenses to converge (focus) or diverge (spread out) light rays, depending on their shape.

Convex lenses, for instance, are thicker in the center than at the edges and cause parallel rays of light to converge to a single point known as the focal point. Conversely, concave lenses, which are thinner in the center than at the edges, cause light rays to diverge. In both cases, it is the refraction of light at the interface of different media that allows the lenses to manipulate light effectively.

This understanding of refraction is crucial in optics, as it is the basis for the functionality of various optical instruments, such as cameras, microscopes, and glasses, where focusing light is essential for forming clear images.