Diffraction pattern

1. Feb 27, 2005

Steph

I'm stuck on the following question:

the diffraction patterns produced when Xrays of wavelength 46.8pm or electrons of energy 688eV are scattered from the same specimen of aluminium are found to be essentially identical. Use this information to determine the value of Planck's constant, h.

I'll let L = wavelength, p = momentum

So far I've calculated the momentum of the electrons using E = (p^2)/2m. I also have converted the Xray wavelength to SI units.

So I know L = h/p thus h = Lp = constant. But I'm not sure what to do from here. Does the fact they have the same diffraction pattern mean that the wavelength of the X-rays is equal to that of the electron beam?

Thanks for any hints you can give me

2. Feb 27, 2005

Steph

Sorry - I've just found the mistakes in my working and have managed to complete the question