Two-wave interference: Young's slits
Light interference - Theory and applications

It was Thomas Young who, in 1801, discovered and correctly interpreted light interference. The experiment gained in luminosity by replacing the two holes with two slits perpendicular to the plane of the figure 1 . Similarly, the source will be replaced by a thin slit parallel to the other two, illuminated with intense light. The S source is a narrow slit, which we'll discuss later in connection with spatial coherence. It illuminates the two slits F ₁ and F ₂ with two waves of the same amplitude and phase if S is on the bisector of F ₁ F ₂ . Each slit diffracts light: the diffraction phenomenon can be interpreted in terms of interference...