A light ray indicates the direction in which a wavefront moves. For some experiments, such as using a magnifying glass, considering light as a ray (geometric optics) is enough to analyze the situation. For other experiments, such as the double-slit experiment, explaining the interference pattern requires considering light as a wave, and the theory of geometric optics is insufficient.
Work Step by Step
Depending on the situation being described and what is being measured, different categorizations make sense.