What does the term 'divergence' refer to in optics?

Divergence in optics specifically refers to the phenomenon where light rays spread apart or move away from each other as they travel. When light rays diverge, they do not converge at a single point; instead, they expand outward, which can be observed in various optical scenarios such as when light passes through a diverging lens or when it emanates from a point source.

This understanding of divergence is crucial in applications such as optical lens design, where knowing how light behaves as it propagates can influence the effectiveness of magnifying glasses, projectors, and other optical devices. This option accurately captures the essential characteristic of divergence, making it the correct answer.

The other options, while related to optics, do not define divergence as precisely. Bending of light rays relates more to refraction, light intensity is a measure of brightness rather than the spatial behavior of rays, and focus of parallel light rays pertains to convergence rather than divergence.