Focal Point (Focus)

Definition

The focal point, also known as the focus, is the point on the principal axis where parallel rays of light converge or appear to diverge from after passing through a lens or reflecting off a mirror.

Related terms

Converging Lens: A lens that brings parallel rays of light together at its focal point.

Diverging Lens: A lens that causes parallel rays of light to spread out as if they came from its focal point.

Principal Axis:

An imaginary line passing through the center of curvature, vertex, and focal points of a lens or mirror.