Homework Help: Basic Quantum Tunneling question

1. Nov 18, 2013

PsychonautQQ

1. The problem statement, all variables and given/known data
A particle of energy E approaches a step barrier of height U. What should be the ratio E/U be so that the reflection coefficient is 1/2.

2. Relevant equations
Transmission + Reflection = 1
Transmission = e^(-2a*alpha)
a = mw∏/h
alpha^2 = (8m∏^2/h^2)(U-E)

Reflection = (k1-k2)^2 / (k1+k2)^2

3. The attempt at a solution
So this is a little bit messy.. I assume most people that are going to help me are familiar with these basic transmission and reflection equations. Anyway is there a possible way to solve this problem an get a ratio that is JUST a number? wouldn't you always have other variables in it since it's talking about a completely undefined particle? there are no ways to get the m's and w's out of the equations right?

2. Nov 18, 2013

Simon Bridge

All those k's depend on energy.
Expand them out in the reflection coefficient and see what happens.