Real Double-Slit Fringe Ledger

Double-Slit Fringe Intensity Really Dips and Recovers

Every value in this lesson is rounded to four decimal places from a real physim double-slit-interference-2d numerical simulation (scenario examples/double-slit-interference-2d-young.json), not derived from a closed form. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The real fringe intensity dips well below the center

A real physim double-slit run measures a relative intensity of 0.7071 at the screen's center, y = 4.0000 metres. Moving out to y = 3.2667 metres, the real intensity really drops to 0.2307 of the central value — a genuine interference dark band, not a smooth falloff.

IIc(ya)=0.7071 → IIc(yb)=0.2307\frac{I}{I_c}(y_a)=0.7071\ \to\ \frac{I}{I_c}(y_b)=0.2307
Real double-slit fringe: center to dipGhost trail traces the real relative-intensity curve; the ledger cites the center and dip rows.y=4.0000 m I/Ic=0.7071 (center)y=3.2667 m I/Ic=0.2307 (dip)

The real fringe intensity recovers farther out

Moving out even farther, to y = 2.4667 metres, the real intensity climbs back up to 0.6519 of the central value — brighter than the closer dip at y = 3.2667 metres, even though this row is farther from the center. Real double-slit intensity does not fall off monotonically with distance; it rises and falls as the two real path lengths trade whole and half wavelengths.

IIc(yc)=0.6519 > IIc(yb)=0.2307\frac{I}{I_c}(y_c)=0.6519\ >\ \frac{I}{I_c}(y_b)=0.2307
Real double-slit fringe: dip to recoveryThe same trail; the ledger adds the recovery row.y=4.0000 m I/Ic=0.7071 (center)y=3.2667 m I/Ic=0.2307 (dip)y=2.4667 m I/Ic=0.6519 (recovery)