Hi(adsbygoogle = window.adsbygoogle || []).push({});

In lab classes today I worked with diffraction gratings, but there is one thing I can't quite seem to understand. If we deal with ruled diffraction gratings, then they are blazed at angle such that the first order is reflected back at the same angle as the incident angle with a specific wavelength, i.e. from the diffraction equation one gets

[tex]

\lambda = \frac{2}{n}\sin \alpha

[/tex]

Here n is the grooves/mm. When I look at a grating at a manufacturer of optical components, I see that some grating is optimized for (actual numbers!) 400nm and is blazed at 13.0155556 degrees. This gives me the wavelength 375.4nm when there are 1200 grooves/mm.

Why can't they blaze the grating at an angle such that λ gives 400nm exactly? (By the way, this is not homework of any kind!)

Best,

Niles.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Diffraction grating lab

**Physics Forums | Science Articles, Homework Help, Discussion**