Electron diffraction - effect of electron wavelength

1. May 5, 2014

Molly1235

Hello, I know how electron diffraction works, and that if you decrease the wavelength of the electrons less diffraction occurs, so the rings are smaller, however was wondering what happens if the wavelength is increased? Is it just the opposite? More diffraction so larger rings?

I was also thinking that perhaps less diffraction happens if you increase the wavelength as well as if you decrease it, as the wavelength is getting further away from the atomic spacing of the graphite or whatever is being used.

Both made sense in my head so I wonder if anyone can help?

Thanks!
Molly :)

2. May 5, 2014

diber

Hello,

The effect of the electron wavelength on the diffraction angles is described by Bragg's law:

n.lambda = 2.d.sin theta

with n the order of the diffraction, lambda the wavelength, d the distance of the diffraction grating (i.e. the distance between crystal planes) and theta the diffraction angle. With this law, you can see immediately the effect of a change in wavelength.