The path difference of two light rays refers to the discrepancy in the distances traveled by those rays when they reach a specific point or interfere with each other. It is a concept commonly used in the study of interference and diffraction of light waves.
When light passes through different mediums or encounters obstacles, it can change direction or undergo diffraction, resulting in the light rays following different paths. The path difference is the numerical difference between the lengths of these paths.
In interference phenomena, such as with Young's double-slit experiment, the path difference determines the phase relationship between the light waves and can lead to constructive or destructive interference patterns. By controlling the path difference, scientists and researchers can manipulate and observe various interference effects in optics.
In summary, the path difference of two light rays represents the variance in the distances they travel, which plays a crucial role in interference and diffraction phenomena.