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Crystal spacing of a solid surface, Bragg's law

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Homework Statement



In a particular Low Energy Electron Diffraction (LEED) study of a solid surface, electrons at 45 eV were diffracted at [tex]\phi[/tex] = 53 degrees. Calculate the crystal spacing d.

Homework Equations



n[tex]\lambda[/tex]=2dsin([tex]\phi[/tex])
[tex]\lambda[/tex] = hc/E
wavelength = c/v
E = vh(n + 1/2)

Note here v is the frequency (nu looked weird on this site)

The Attempt at a Solution



This questions comes from a problem in my textbook that was a recommended practice problem for an upcoming exam. Despite being an odd numbered problem the answer to it wasn't in the back of the book (figures). Anyways I just wanted to make sure I was solving it correctly.

Firstly I converted the 45 electronvolts into 7.209765E-18 Joules
Then by wavelength = hc/E, i found the wavelength to be 2.754E-8 Meters
Then I found the frequency to be 1.089324619E16 s-1
Next I found n to be 1/2 (which is weird cause I thought it would be an integer)
Lastly I plugged these values into bragg's law and got 8.623E-9 Meters

Like I said the answer was not in the book for some reason and I'd like to know if I'm doing this right
 

Answers and Replies

  • #2
674
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You need to show your steps better. Also, why are you using the last equation listed? That is for a quantum harmonic oscillator. In this case you just have diffraction.
 

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