Science & Engineering · Optics, Photonics & Acoustics
Diffraction Grating Fringe Angle & Spectral Resolution Calculator: inputs, method, and how to read the result
Solve the grating equation d·sin(θ) = m·λ for optical spectroscopy.
Choose inputs for the case you are checking
The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.
- Grating Lines Per Mm: Diffraction grating ruling density in lines per millimeter.
- Wavelength Nm: Incident light wavelength (λ) in nanometers.
- Diffraction Order M: Diffraction order integer (m = 1, 2, ...).
What the calculation includes
With the default values shown, Diffraction Order Angle (θ_m) is 18.61 deg. The calculation follows Diffraction Grating Physics & Engineering Equation; the formula and variable definitions above show how the inputs combine.
One-input check: With the other defaults held constant, changing Grating Lines Per Mm from 600 lines/mm to 660 lines/mm changes Diffraction Order Angle (θ_m) from 18.61 deg to 20.56 deg. This is a comparison inside the calculator's stated model, not a prediction.
Where to use caution
- Uses standard SI physical constants (g = 9.80665 m/s², c = 299,792,458 m/s, σ = 5.670374×10⁻⁸ W·m⁻²·K⁻⁴).
- Engineering reference model; apply appropriate safety factors and empirical calibration for critical hardware designs.
Scope: SI / NIST Physics & Engineering Standard Check the assumptions and limitations against your situation before relying on the estimate.
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