# Homework Help: Electric Potential and Wave Nature of Matter

1. Feb 7, 2013

### quicksilver123

1. The problem statement, all variables and given/known data
An electric potential difference accelerates electrons from rest position towards a screen.
Just before striking the screen, the electrons have a wavelength of 1.0*10^-11 m
Find the electric potential difference.

2. Relevant equations

p=h/λ
ΔEK=qΔV

3. The attempt at a solution

p=h/λ
mv=h/λ
v=h/λm
v=(6.63*10^-34)/((1.0*10^-11)(9.11*10^-31))
v=72777167.95 m/s

ΔEK=qΔV
EK2-EK1=eΔV
0.5(9.11*10^-31)(72777167.95)^2 - 0.5(9.11*10^-31)(0)^2 = eΔV
ΔV=0.5(9.11*10^-31)(72777167.95)^2 / e
ΔV=15078.51948 V

Is this correct? (other than significant digits)

Last edited: Feb 7, 2013
2. Feb 7, 2013

### Staff: Mentor

Once again your v=(6.63*10^-34) / ( (1.0*10^-11) * (9.11*10^-31) )equation needs some parens

and your v result needs to be significant figure adjusted to be 7.28 x 10^7 m/s

similarly for the delta v result.

Again the physics looks right but someone at PF needs to second it for me.

3. Feb 7, 2013

### quicksilver123

fixed.

the question wasn't asking for velocity so i didn't round it in order to get a more accurate result for electric potential difference