## Fall 2013 Midterm #4

$\lambda=\frac{h}{p}$

Michael Lonsway 3O
Posts: 43
Joined: Wed Sep 21, 2016 2:57 pm

### Fall 2013 Midterm #4

During spontaneous fission uranium-235 emits a neutron with a mass of approximately 1.00866g/mol. If one of these neutrons has an energy of 4.84 Mev, what is its de Broglie wavelength?
In your solution use E=p^2/2m and explicitly show that kinetic energy is related to momentum.

I'm confused with what the question is specifically asking for an how E=p^2/2m is related to the de Broglie equation: λ= h/p

Chem_Mod
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### Re: Fall 2013 Midterm #4

They are asking you to write E in terms of the de Broigle wavelength. The de Broigle wavelength is $\lambda = h/p$ , which can be written as $p=h/\lambda$. Plug this in for the p2 term in the kinetic energy equation.

Josue_Marin_3I
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Joined: Wed Sep 21, 2016 2:56 pm

### Re: Fall 2013 Midterm #4

Are we expected to be able to do simple derivations of formulas like in this problem for the midterm? :)

Joseph Nguyen 3L
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Joined: Fri Jul 22, 2016 3:00 am

### Re: Fall 2013 Midterm #4

I think it's safer and probably better if you have time to do those derivations. For example, $E = hc/\lambda$ is not an equation given to you, so we should not assume that you can get it just like that. I'm pretty sure listing E = hv and c = v*$\lambda$ is enough to show that your first equation wasn't out of nowhere.