By Zencalcy Editorial TeamLast reviewed About us
A diffraction grating has thousands of parallel grooves that split light into sharp, widely separated orders. The angle of each order depends on the wavelength and the groove spacing, which is why gratings outperform prisms in spectrometers.
Diffraction angle from groove spacing and wavelength.
d sin θ = m λ d = 1 / N
d is the groove spacing in metres, θ the diffraction angle, m the order and λ the wavelength. N is the line density in lines per metre.
| Symbol | Meaning |
|---|---|
| d | Groove spacing, the reciprocal of line density. |
| θ | Diffraction angle from the normal. |
| m | Diffraction order, an integer. |
| λ | Wavelength of the light. |
d = 2 µm, so sin θ = 0.275 and θ = 15.96°. The second order appears at 33.37°, and the third at 55.6°.
Continue with the Double Slit Interference Calculator, Field of View Calculator, or the Hyperfocal Distance Calculator — or browse more optics and light tools and all physics calculators.
Thousands of slits interfere constructively only very close to the exact order angle, so each wavelength forms a narrow line rather than a broad band.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026