Solving Diffraction Problem with Angle of Deviation & Second Order

[Jchem]

I have no idea where to start here..

this is the only question in this unit that has an angle in it... also not sure what second order means.

the angle of deviation of light of 400 nm wavelength is 30 degrees in second order. How many lines per cm are there on this diffraction grating if N = 1/d






any tips on how to get started?

thanks

 

[Adrian Baker]

You want the Diffraction grating equation:

n*lamda = d sin(theta)

n = 2 (in your case) as it is second order.
lamda = wavelength
d = spacing on diffraction grating

 

[Chi Meson]

THe "order" is referring to which "dot" or "fringe" of light you are looking at. When a beam shines through a diffraction grating, the dot that appears along the straight line path from the beam is the "central" or "zeroth" order. The closest dots on either side of the central dot are called "first order," and the next are called second, third, etc.