# Electron and matter waves: WE NEED HELP

1. May 25, 2009

### afcwestwarrior

Electron and matter waves: WE NEED HELP!!!

1. The problem statement, all variables and given/known data
Calculate the de Broglie wavelength of (a) a 1.00Kev electron, (b) a 1.00Kev photon, and (c) a 1.00KeV neutron

2. Relevant equations
K = mv^2 / 2

p = mv

p = sqrt 2KM

m of electron is 9.11 * 10^-31 kg

1 ev = 1.6 * 10^-19 Joules

change in Lamda = h / p

h = 6.63 *^-34

3. The attempt at a solution

Is this correct. Here's what we tried.
)
change in lamda = 6.63 * 10 ^ -34 / sqrt(2) ( 9.11 * 10 ^-31) ( 1KeV) (1000eV / 1Kev) (1.6 * 10 ^ -19 J)

=

=

2. May 25, 2009

### Redbelly98

Staff Emeritus
Re: Electron and matter waves: WE NEED HELP!!!

Looks like you are setting things up okay. So what is the result of your calculation?

A couple of minor points:
The energy and mass belong inside the sqrt(), it's not clear if you are meaning to do that from what you wrote.
The "J" at the end of your expression should really be "J/eV" to do the units conversion properly.