I basically am having a problem understanding the units used on the atomic level such as MeV/c and MeV/c^2.(adsbygoogle = window.adsbygoogle || []).push({});

I have a problem where I have a given energy of 370 MeV for a photon.

This means the wavelength is

[tex]\lambda = \frac{{(6.6261*10^{ - 34} )c}}{{(3.7*10^8 eV*\frac{{1.6022*10^{ - 19} J}}{{1eV}})}}[/tex]

[tex] \lambda = 3.35*10^{ - 15} m[/tex]

The photons momentum is also given by…

[tex] \begin{array}{l}

p = \frac{{6.6261*10^{ - 34} }}{{3.35*10^{ - 15} m}} = \frac{h}{\lambda } \\

p = (1.978*10^{ - 19} kg*m/s)(\frac{{1\frac{{MeV}}{c}}}{{5.344*10^{ - 22} \frac{{kg*m}}{s}}}) = 370\frac{{MeV}}{c} \\

\end{array}[/tex]

This begs the question, did I screw up and get into some circular logic or is the energy in MeV/c^2 the same number as the momentum is in MeV/c for photons?

Also, in these units, I need to determine what an equivalent particle's would be with that total energy and momentum. I used…

[tex]\begin{array}{l}

E^2 = p^2 c^2 + m^2 c^4 \\

m^2 c^4 = E^2 - p^2 c^2 \\

m^2 = \frac{{E^2 }}{{c^4 }} - \frac{{p^2 }}{{c^2 }} \\

m = \sqrt {370^2 \frac{{MeV^2 }}{{c^4 }} - 370^2 \frac{{MeV^2 }}{{c^4 }}} \\

\end{array}[/tex]

Obviously I did something wrong… Doesn't c = 1 somewhere?

Where did I go wrong?

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# Homework Help: Atomic scale unit conversions

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