Double Slit Experiment and Wave Interference Simulator

How the double slit experiment works

Two narrow slits illuminated by one monochromatic wave produce evenly spaced bright bands. The spacing follows from path difference; each slit's finite width controls how bright the outer bands remain.

Wave interference: adding two waves

Interference is addition. A whole-wavelength path difference adds crest to crest, while a half-wavelength difference cancels. The two-source mode shows that same rule without a slit envelope.

Single-slit diffraction and the envelope

Each slit spreads light on its own. That diffraction envelope is plotted beside the interference term, so their product is visible on the same axes.

Missing orders

An interference maximum disappears when it lands exactly on a diffraction minimum. The calculation keeps the entered decimal widths as exact rational values when identifying that condition.

Where the small-angle formula fails

The table prints both y = m lambda L / d and the exact flat-screen geometry. Their difference is reported in micrometres for every listed order.

Diffraction gratings and resolving power

A grating is the same interference calculation with many illuminated slits. When peaks become narrower than a meaningful sampled curve, the instrument uses analytically placed line-spectrum peaks and a distinct two-uniform deterministic stream.

Single photons and the build-up pattern

Each detection is one point. Repeating the seeded sampling builds the same distribution predicted by the analytic intensity curve.