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Here is the problem, I think I may be stuck but I'll provide all the information I have so far.

White light (400-700nm) is incident on a 600 line/mm diffraction grating. What is the width of the first order rainbow on a screen 2.0m behind the grating?

What I figured was to use the equation d*sin(theta) = m * wavelength

as well as the equation y = L*tan(theta), with L = 2.0m, m = 1 (first order rainbow),

Basically, I have to find theta, then find y, which ends up being the width of my projected rainbow. I am, however, totally stuck at this point. I'm not even sure if my assumption that m = 1 is right, or if I am on the right path.

Any help in the right direction would be awesome.

Thank you

twiztidmxcn

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# Homework Help: Diffraction grating white light problem

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