Speed of electron after collision with Photon

[dcl]

Heya's..

Im stuck on the following question and I can't seem to arrive at the answer at the back of the book.

X-Rays from Palladium with a wavelength of 0.0590 nm, are scattered backwards from collisions with electrons. The X-Rays that return along their original path have a wave length of 0.0639nm.

I've used DeBroglies formula to calculate the momentum of the incoming and outgoing photons. But I'm not reallty sure what to do at this stage.. Any help would be wonderful.

Thanks :)

 

[HallsofIvy]

Okay, you know the change in momentum of the photons and you know that momentum is conserved in this collision. Any momentum the photons have lost is gained by the electrons.

 

[dcl]

Originally posted by HallsofIvy
Okay, you know the change in momentum of the photons and you know that momentum is conserved in this collision. Any momentum the photons have lost is gained by the electrons.

Hmm
So basically the Momentum of the Incoming Photon is equal to the Momentum of the outgoing photon PLUS the momentum of the electron??

and then i just solve for the electrons velocity..

I could have swore I did a calculation like this..
Perhaps its wrong.. or it could be a mistake in the answer book or something.