- #1

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- Homework Statement
- Derive the equation

- Relevant Equations
- E=P^2/2m

I am having trouble understanding this derivation and need some guidance.

1) I tried solving the algebra from the first equation to the second equation circled in red. Can someone please help with what algebra steps, I cannot solve to the circled solution.

2) What does E

_{e}stand for? Is it Total energy of the electron?

3) Where did the value 5.49x10

^{-4}come from? This does not appear to be the mass of the electron.