Physics

Calculate diffraction-limited angular resolution from aperture and wavelength. Compare Rayleigh, Dawes, Sparrow, and convert to arcsec or detail size.

Calculate circular aperture area from diameter or from focal length and f-number. Convert units and compare light-gathering ratios and stops.

Estimate distance using a mil or MOA reticle. Use target size or the horizon method, plus optional SFP magnification correction.

Solve the grating equation for angle, wavelength, spacing, or line density. Includes incidence angle, sign convention, and order feasibility checks.

Convert between diopters and focal length, combine two lens powers, and (optionally) estimate magnifier power with clear sign handling.

Find the horizon distance from your height, with optional refraction and target visibility. Outputs surface and line-of-sight distances.

Calculate refractive index from light speed, or light speed from n. Use Snell’s law mode to solve angles and detect total internal reflection.

Compute laser beam divergence from two spot sizes and distance. Choose full or half angle, units, and compare to a Gaussian limit estimate.

Compute beam diameter and divergence after a beam expander, or solve for magnification or focal length with full vs half-angle controls.