What does a wavefront represent in optics?

A wavefront represents an imaginary surface in which all points are in phase with each other, meaning they are oscillating together at the same stage of their wave cycle. In optical terms, this concept is pivotal for understanding how waves propagate through different media. When light travels, it does so in wave form, and the wavefront serves as a tool to visualize the propagation direction of these waves.

For example, in a plane wave, the wavefronts are flat surfaces perpendicular to the direction of wave propagation, while in spherical waves emitted from a point source, the wavefronts are concentric spheres. Recognizing wavefronts is essential in optics, as it helps explain phenomena such as reflection, refraction, and diffraction, which depend on how these surfaces interact with various optical elements.

In contrast, other concepts such as a point of light emission, the physical boundary of a lens, or measurements of light intensity do not capture the wave nature of light in the same way and therefore do not accurately describe what a wavefront represents in the context of optics.