Diffraction Grating Help

A diffraction grating has 600 lines/mm. Yellow light from a street lamp is shone onto the grating. The yellow light contains two main wavelengths - of 589.6 nm and 589.0 nm. Calculate the angular separation of the second order (n=2) of these two components as they emerge from the grating. Give your answer to 2 significant figures.

I understand that the point of diffraction grating is to separate wavelengths, however I'm not sure how to apply that to this question. I don't need someone to solve it just a push in the right direction.
Thanks in advance.

Reply 1

lizardlizard

You should be familiar with, and able to calculate angles from the formula

It would really help in this question to draw a diagram of what is happening - you are being asked to calculate the angle between each beam leaving the grating. Since the wavelengths are obviously very similar, this difference will probably be very small. Think about the relationship between the red, blue, and green angles in this diagram.