Fall 2013 Midterm #4

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Michael Lonsway 3O
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Fall 2013 Midterm #4

Postby Michael Lonsway 3O » Sat Oct 29, 2016 6:03 pm

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

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Re: Fall 2013 Midterm #4

Postby Chem_Mod » Sun Oct 30, 2016 6:57 pm

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

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Re: Fall 2013 Midterm #4

Postby Josue_Marin_3I » Sun Oct 30, 2016 10:05 pm

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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Re: Fall 2013 Midterm #4

Postby Joseph Nguyen 3L » Mon Oct 31, 2016 11:42 am

I think it's safer and probably better if you have time to do those derivations. For example, 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* is enough to show that your first equation wasn't out of nowhere.

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