How Is the Diffraction Angle Calculated for Different Wavelengths?

[MarcL]

Homework Statement

A grating places a spectral line of wavelength 681 nm at 12 degrees in first order. At what angle is a line of wavelength 439 nm observed in second order?

Homework Equations

I believe dsinθ= mλ

The Attempt at a Solution

This is where I get lost, I can solve for every problem in difraction ( We did Rayleigh's criterion, double slit / single slit difraction) but I can't seem to be able to start a problem that involves grating, any pointers on how to start would be nice ^^ I just want to know how to approach the problem! :)

 

[TSny]

As far as finding the angles for the bright fringes, there is no difference between a grating and a double slit.

One approach to this problem would be to use the information about the 681 nm line to determine the distance d between two slits in the grating.

 

[MarcL]

Ah, it worked. Thanks a lot ^^ Just a little question, if you don't mind answering it of course. If ever it asked me to look for the distance between the two waves, would I need to compare the equations or something?

 

[TSny]

Ah, it worked.

Good!

If ever it asked me to look for the distance between the two waves, would I need to compare the equations or something?

I'm not sure what you mean by "distance between the two waves". Can you clarify that?