# Barrier Penetration

I have a question to do but im a bit confused about one thing. It invloves protons penetrating a barrier. The protons ae quoted to have a KE in the units of eV (which i will have to convert to joules in order to work in SI units). However the barriers height is given in volts. I assumed this height should be in the units of energy so i multiplied the heigh (in volts) by the charge of a proton/electron, however i get a silly answer at the end...

The formula i am using is for the transmission coeff, it involves a sinh squared term, its too complicated to write here, i have seen a website with it but i cant find the link, however i dont think this is the problem...

thanks for any replies

to clarify the "silly answer" is not to do with the volts expressed as energy but its to do with the question i have to do...

turin
Homework Helper
zeta,
I'm confused about what is confusing you. It seems that you never explicated your confusion.

You don't have to work in Joules. In fact, it would probably be more convenient to work in eV (as evidenced by the potential being given in V). I will assume that the protons have less energy than the barrier height? So, maybe you're confused by how they get through? I will also assume that the barrier has some finite width? In this case, the protons get through because they are already through to begin with. That is, their wave function exists on the other side of the boundary because it satisfies Schroedinger's eq. that way.

Maybe your confused by getting a negative kinetic energy inside the barrier potential? That's normal.