## De Broglie Equation

Emily Mei 1B
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### De Broglie Equation

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.

Chem_Mod
Posts: 18150
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 423 times

### Re: De Broglie Equation

$E=hv$ 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.

Magdalena Palavecino 1A
Posts: 54
Joined: Fri Sep 29, 2017 7:04 am

### Re: De Broglie Equation

When do we use 1/2mv2 for Ek and when do we use de broglies equation for Ek?

Chem_Mod
Posts: 18150
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 423 times

### Re: De Broglie Equation

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.