What do we call a light ray that travels into a reflecting surface?

A light ray that travels into a reflecting surface is specifically termed an "incident ray." This is the ray that approaches and strikes the surface before any reflection occurs. When the incident ray hits the reflective surface, it interacts with that surface, leading to a phenomenon known as reflection, where some of the light is bounced back.

Understanding the role of the incident ray is crucial in optics, as it sets the initial parameters for determining the angle of reflection, which adheres to the law of reflection stating that the angle of incidence equals the angle of reflection. Other terms like "reflected ray" refer to the light that bounces back from the surface, while "refracted ray" indicates light that has passed into a different medium and changed direction. The term "transmitted ray" describes light that travels through a medium without being absorbed or reflected. Thus, identifying the incident ray is key in analyzing how light behaves when interacting with different surfaces.