Double-Slit Fringe Spacing Calculator

Convert wavelength and separation to metres, multiply wavelength by screen distance, and divide by slit separation. This linear spacing is distinct from a single-slit envelope minimum angle. The calculator evaluates only the stated idealized equation and supplied values. It does not infer missing conditions, choose an experimental convention, or certify a measurement. Keep every quantity in the displayed unit and verify the model against the physical setup before relying on the result.

The output is the approximate center-to-center separation of neighboring bright or dark fringes near the axis. Large off-axis positions need exact trigonometric geometry rather than constant spacing. Numerical precision does not imply experimental accuracy. Compare the output with scale, sign, limiting cases, and an independent source, then account for uncertainty in measured inputs and constants before using it in laboratory, engineering, or safety-sensitive work.

The screen is far away, angles are small, slits are coherent, and spacing is center to center. It excludes slit-width envelopes, unequal amplitudes, finite coherence, medium dispersion, and detector sampling. The result is educational and is not a simulation, calibration, engineering approval, or safety determination. More complete models may require geometry, material response, boundary conditions, relativistic frames, dispersion, losses, uncertainty propagation, or numerical field solutions not represented by these inputs.