# Homework Help: Photoelectric effect

1. Mar 20, 2010

### Sassenav22

1. The problem statement, all variables and given/known data
What potential difference must be applied to stop the fastest photoelectrons by a nickel surface under the action of ultraviolet light of wavelength 220 nm? work function of nickel is 5.00eV.

2. Relevant equations
h[c]/[$$\lambda$$] = $$\Phi$$ + eV

3. The attempt at a solution
h=6.6x10^-34 Js
c=3.0x10^8 m/s
$$\lambda$$=200x10^-9 m
$$\Phi$$=5.00eV
e=1.6x10^-19
V=?

[6.6x10^-34(3.0x10^8)]/[/200x10^-9] = 5.00 + 1.6x10^-19V
9.9x10^-37 = 5.00 + 1.6x10^-19V
9.9x10^37/5.00 = + 1.6x10^-19V
1.98x10^37 / - 1.6x10^-19 =V
v= 1.23x10^.18m/s

not sure if this is right

Last edited: Mar 20, 2010
2. Mar 20, 2010

### kuruman

You need to convert the work function from eV to Joules before you plug it in.

3. Mar 20, 2010

### physics girl phd

Also: really watch your units. As you have the equation solved... you're giving an answer in m/s... which doesn't make any sense. Carry your units along with the math... the problem is looking for a potential difference (and the solution should therefore be in volts).

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