# Electron Scattering Question

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1. Nov 1, 2015

### jecyca2003

1. The problem statement, all variables and given/known data
A beam of electrons with kinetic energy 50 eV is fired at a 100 nm thick crystalline nickel foil.
1. (a) Calculate the speed of the electrons in the beam.

2. (b) Based on your answer to part (a), state, with justification, whether classical (Newtonian) mechanics correctly describes this system.

3. (c) Determine the de Broglie wavelength of the electrons.

4. (d) Electrons incident on the nickel are scattered. The scattered electrons show strong peaks in intensity at particular orientations of the incident beam to the nickel target. Explain, with the aid of a detailed sketch, how this can be accounted for.

The energy of the electrons is now increased to 50 MeV.
1. (e) Repeat (a)-(c) above for these electrons, and from your results explain why the majority of electrons pass straight through the foil. You may find it useful to know that hc/2π = 197 MeV fm.

2. (f) Occasionally one of the beam electrons elastically scatters from an atomic electron in the foil. Is momentum conserved in such reactions? Explain in words why the products of the reaction are not emitted at 90 degrees to one another.
2. Relevant equations
KE = 1/2 (m)(v^2)
λ = h/√(2KEm) (deBroglie Wavelength Equation)
3. The attempt at a solution
For part a) and c), I just plugged the numbers into the equation. I am not quite certain why the question emphasizes 100nm.

I am stuck mainly with the second half of the question d), e), and f). It would be very nice to get some help for those questions.

Last edited: Nov 1, 2015
2. Nov 1, 2015

### Paragon Hardy

look up the davisson gemer experiment. the peaks correspond to constructive interference from the scattered electrons.

Last edited: Nov 1, 2015
3. Nov 1, 2015