### 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.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=27&t=22269

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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.

Posted: **Sun Oct 15, 2017 6:14 pm**

We will start with two fundamental equations

and

Next, we will set these equations equal to each other giving us

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.

and

Next, we will set these equations equal to each other giving us

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.

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?

Posted: **Mon Oct 16, 2017 11:05 pm**

De Broglie's equation relates wavelength with mass and velocity, not energy. E_{k} is defined by . 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.