Double Slit Question: Find Angular Separation for m=2, 412 nm, 349 l/mm

[metalmagik]

Homework Statement

A grating with 349 lines/mm is illuminated with light of wavelength 412 nm What is the angular separation between the two lines formed in order m=2?

Homework Equations

\vartheta = m\lambda/d

The Attempt at a Solution

I did not know how to use this equation successfully since I did not have d. I do not know what the 349 lines/mm has to do with anything, so that is obviously what I'm missing. Help!

 

[Stonebridge]

This is not a "double slit" question, it is a diffraction grating question, for which there is an appropriate equation. (Not the one you give)
d is the separation between the lines in the grating and is calculated from the number of lines per mm that is given by a simple inverse relationship.

 

[Redbelly98]

That's okay, in diffraction problems the same equation is used for a diffraction grating and the double slit . (You can click on the terms "diffraction grating" and "double slit", in that previous sentence, for more info.)

There are 349 line spacings in 1 mm. Therefore, the distance between 2 adjacent lines is ___?

 

[metalmagik]

1/349! So that is equal to d? I worked the problem out for \vartheta and I'm getting like .28, the multiple choice answers are 26, 40, and 33^{o}...