# Simple De Broglie Wavelength Problem

1. Mar 11, 2005

### vsage

I have the formula for the de Broglie wavelength but for some reason I'm not using it properly. Here's the question:

What is the De Broglie wavelength (in nm) of a proton with a kinetic energy of 10 eV? (Take the mass of a proton to be 938 MeV/c2.)

$$\lambda = \frac{hc}{pc}$$

hc = 1239.8 nm*eV
$$pc = \sqrt{{KE}^2 + 2KEm_0c^2}$$ which should be around 101.5 eV, so the answer would be 12.2nm which is wrong! What did I do wrong? It should have been a simple plug and chug problem after deriving pc in terms of KE and the rest mass.

Last edited by a moderator: Mar 11, 2005
2. Mar 11, 2005

### vsage

Nevermind! Apparently in my crazy mind 0.511MeV = 511eV

3. Mar 11, 2005

### dextercioby

What would you need that number?

Daniel.