Equations · equation

Diffraction Grating Equation

Waves & Optics · 1821

Equation: d·sin θ = m·λ
Field: Waves & Optics
Named After: Joseph von Fraunhofer
Symbols: d spacing between the grating's slits or grooves · θ angle of the bright beam · m order (0, ±1, ±2, …) · λ wavelength of the light
Year: 1821

Significance

Many slits in lockstep fling each wavelength to its own angle — light sorted by color with ruler-like precision. Fraunhofer used it to map the Sun's dark spectral lines; gratings still sit at the heart of every spectrometer, and a CD's rainbow is the equation at play.

Minerals

Theories

Wave Theory of Light

Related

Bragg's Law Gaussian Beam Divergence Cosmological Redshift Fourier Transform Rydberg Formula

Instruments

Keck Observatory James Webb Space Telescope (JWST)Very Large Telescope (VLT)

Requires

Trigonometric Ratios Wave Speed

Elements

Sodium Hydrogen

Referenced by

element

Hydrogen Sodium

equation

Bragg's Law Cosmological Redshift Fourier Transform Gaussian Beam Divergence Rydberg Formula Trigonometric Ratios Wave Speed

instrument

James Webb Space Telescope (JWST)Keck Observatory Very Large Telescope (VLT)

theory

Wave Theory of Light

Open on the Equations shelf — the interactive card, the filters, and everything alongside it.

From the Equations database in Notion, last edited 2026-08-26. This page is the row, rendered by the build; nothing on it is written by hand.