Diffraction is closely related to Huygen's principle, which treats each propagating wave as pulsating wavefronts along its incident path. When a wave encounters an opening comparable to its own wavelength, the opening will act as a source, "diffracting" through the opening. Disregarding the quantum-mechanical aspects of light(insert a footnote explaining why we can disregard it), light diffracting through a slit will emit another wavefront at every point along the wavefront, causing interference. Diffraction and interference go hand in hand; Richard Feynman once claimed "diffraction tends to be used when referring to many wave sources, and interference when only a few are considered." The propagating wavefronts that originate from the wavefront, which originates from a single slit or opening, interfere constructively or destructively according to their relative path lengths with one another. One can simplify the stemming wavefront phenomena by separating the slit into multiple openings, where the path length difference can be found by comparing the angle separation of each opening at a single point a distance L away. Constructive interference occurs when the waves superimpose upon one another, building upon their intensities. Destructive interference also stems from the superposition of waves, but their path length difference causes their intensities to subtract rather than add.