1. The problem statement, all variables and given/known data Griffiths Intro Quantum Mechanics free particle question. Normalize wave function, find Phi(k), Psi(x,t), and comment on its behavior for small and large a. The wave function given is Ae-a|x| 2. Relevant equations 3. The attempt at a solution I found the correct Phi(k), but for the small a vs large a, I don't understand why Phi(k) corresponds to momentum. I see that there is a small spread with a sharper peak in Psi with a flatter, more spread out Phi, and a flatter more spread out Psi with a sharper, smaller spread Phi, but I don't see how this is an example of the uncertainty principle. I don't see from reading Griffiths how Phi is any indication of momentum.