Diffraction Grating Calculator: Wavelength from ...

What is a Diffraction Grating?

A diffraction grating is an optical component with a large number of parallel, equally spaced slits (or grooves). When light passes through, each slit acts as a wave source, and the resulting interference pattern separates the light into its component wavelengths. This is the basis for spectrometers — instruments that measure the spectrum of light.

🌈 Diffraction Grating Calculator

Use our free calculator for instant, accurate results.

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📐 Formula

d × sin(θ) = m × λ

d = grating spacing (m), θ = diffraction angle, m = order (integer: 1, 2, 3...), λ = wavelength (m).

📝 Worked Example

A grating has 500 lines/mm → d = 1/500,000 = 2×10⁻⁶ m
First order (m=1) maximum at θ = 15°:
λ = d×sin(θ)/m = 2×10⁻⁶ × sin(15°) = 517 nm (green light)

📝 How to Use the Calculator

Enter Grating SpecificationInput lines per mm or grating spacing d in nm.

Enter Diffraction OrderUsually m=1 (first order) for brightest maximum.

Enter Angle or WavelengthProvide either to calculate the other.

View ResultsSee the corresponding wavelength and color of visible light if applicable.

❓ FAQ

What is the difference between a diffraction grating and a prism?

Both separate white light into a spectrum, but a grating uses interference while a prism uses refraction. Gratings provide linear dispersion and are more useful in spectroscopy.

What does "lines per mm" mean on a grating?

It specifies how many slits (grooves) exist per millimeter. More lines = smaller d = greater angular dispersion.

What is a Diffraction Grating?