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### De Broglie Equation

Posted: Sun Oct 15, 2017 5:45 pm
Would anyone be able to explain/go through the derivation of the De Broglie equation? I know we don't necessarily need to know it but it would help my understanding.

### Re: De Broglie Equation

Posted: Sun Oct 15, 2017 6:14 pm
$E=hv$ and $E = mc^{2}$
Next, we will set these equations equal to each other giving us
$hv = mc^{2}$
From there you can substitute c (speed of light) for v, because the De Broglie Equation applies to all matter. Finally, convert mv to p, because momentum is defined as
mass x velocity, and solve for h.

### Re: De Broglie Equation

Posted: Mon Oct 16, 2017 9:44 pm
When do we use 1/2mv2 for Ek and when do we use de broglies equation for Ek?

### Re: De Broglie Equation

Posted: Mon Oct 16, 2017 11:05 pm
De Broglie's equation relates wavelength with mass and velocity, not energy. Ek is defined by $\frac{1}{2} m v^{2}$. If you're asking when do we use which when given velocity, then that depends on what you're given and whether you're trying to find wavelength or kinetic energy.