Work out double slit interference instantly with clear inputs, formula shown and shareable results.
Young's double slit produces evenly spaced fringes with separation lambda.L/d. Helium-neon light at 632.8 nm through 0.25 mm slits, viewed 2 m away, gives 5.06 mm between bright fringes. Closer slits spread the pattern out, which is why the effect is easier to see with fine slits.
Fringe spacing
y = lambda L / d
Bright fringe condition
d sin(theta) = m lambda
Because spacing goes inversely with d. Wide slits crowd the fringes together until they are unresolvable.
That light interferes, so it behaves as a wave. Repeating it with single electrons is the classic demonstration of quantum superposition.