## HW Question 1.B.19

$c=\lambda v$

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### HW Question 1.B.19

I know for photo-ejection you use the formula Ek= .5m(e)v^2, but how would you approach this problem? Also, when do you use the de Broglie relation?

Rebecca Epner 4A
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Joined: Sat Aug 17, 2019 12:18 am

### Re: HW Question 1.B.19

For this problem, you are expected to know the masses of both a proton and a neutron (you can probably find them in the chapter). Then substitute these values into the de Broglie relationship to calculate both wavelengths (they should be equal for 3 sig figs)

Sharon Rodriguez 3H
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Joined: Wed Nov 14, 2018 12:18 am

### Re: HW Question 1.B.19

This question is asking you to calculate the wavelength of each particle (proton & neutron) when travelling at 2.75 x10^5 m.s^-1 and report the difference as a percentage of wavelength of the neutron. First off, you would use λ=h/mv as we are trying to find the wavelength. First, use this equation with the mass of a proton (which should be given in the book). Then, use the same equation but substitute in the mass of a neutron (should also be given). You will notice the numbers are very similar. The wavelength for both will be identical up to a certain amount of sig figs which will be your answer. You use De Broglie's reaction when trying to solve for the wavelength of things that have a real resting mass (like electrons).

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