# Diffraction grating with combination light

1. Oct 3, 2013

### Hapablap

Green and orange light pass through a diffraction grating that contains 6000 lines/cm. Compare the appearance of the fringe at m = 0 with all the others.

So far I've only dealt with light with one wavelength, so I just want to make sure I have the right thought process here for two wavelengths.

Where m = 0 there is no diffraction, so we should see a combination of green and orange light there, while the other fringes will be either green or orange. With one wavelength, the intensity of all of the fringes is the same (if I'm not mistaken). With two wavelengths, the central maximum will have twice the intensity as the others, because it have 2 wavelengths striking it instead of 1. Then with 3 wavelengths, the central maximum will have three times the intensity, and so on.

Do I have the right idea here?

2. Oct 3, 2013

### Simon Bridge

That's the right way to go - it's the superposition principle.
You have not been told the relative intensities of the green and orange light though.