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Astronomy & optics

Diffraction angle of an optical grating

Find the angle of a diffraction order from wavelength and the line density of an ideal grating.

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01

Your inputs

The starting values are an example.

Use a whole number: 0 is the central order; negative orders are on the opposite side.

Decimals: 12.5 · Thousands: 1,234.56. Follow the field instructions for lists.

02

Your result

Enter your values and select Calculate.

Your calculation will appear here.

Your result will include the relevant values and units.

Understand the calculation

Formula and example

How it is calculated

d × sin(θ) = m × λ; d = 1 mm/line density

Worked example

500 nm light at a grating with 600 lines/mm gives a first-order angle of approximately 17.46°.

Things to check

  • The light is assumed to strike the grating normally.
  • If |mλ/d| exceeds 1, the order is geometrically impossible.

Sources and references