Two sources,
and the still lines
Where the path difference is a whole number of wavelengths the crests arrive together and the surface heaves. Half a wavelength out and they cancel exactly — those calm channels stay flat no matter how long you wait. Drag the sources apart and count them appear.
whatTwo point sources on a surface, summed with distance falloff. The mesh is the live displacement; the curves on the floor are where the two waves cancel exactly.
lawCrests reinforce where the path difference is a whole number of wavelengths, and cancel at half-integer values. The cancellation curves are hyperbolae with the sources as foci.
tryDrag the sources apart, then shorten the wavelength.
noticeMore nodal channels appear as separation grows in units of λ — spacing is set by the ratio of the two, never by either alone.
in lifeNoise-cancelling headphones and antenna arrays are engineered nodal lines.
found byThomas Young, 1801, arguing for the wave theory of light against Newton's corpuscles.