Question

A grating has 1090 lines per centimetre, and a flat screen is perpendicular to the ray that makes the central peak of the diffraction pattern. The screen is 3.55 m from the grating. If light of two wavelengths, 645 nm and 650 nm, passes through the grating, what is the separation on the screen between the third-order maxima for the two wavelengths?

Answer 1

I was never too good at E&M.
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