# Tunneling w/ unknown energy

## Homework Statement

The work function (energy needed to remove an electron) of gold is 5.1 eV. Two pieces of gold (at the same potential) are separated by a distance L.

For what value of L will the transmission probability for an electron to cross from one to the other be T ≈ 10-3? Assume that G = 1 in the formula for the tunneling probability.

## Homework Equations

T $$\approx$$ G*e-2KL
where K=2*pi*$$\sqrt{((2*m)/h2)*(Uo-E))}$$

T: Tunneling Probability
m: Electron Mass
Uo: Potential (the work function in this case)
E: Energy of the electron
L: Length of the potential barrier to tunnel
h: Planck's constant

## The Attempt at a Solution

It seems to be a simple plug and chug, but how do I find the energy to use in the (Uo-E) part in the tunneling equation?