The Heisenberg uncertainty principle, while normally presented in physics circles, is actually a mathematical absolute. A general rule of thumb for light (waves in general really) is high frequency waves propagate in straight lines, and low frequency waves spread out. To get the probability from the wave function, all you have to do is square the wave function. So, there’s the Heisenberg uncertainty principle: . The difference comes about because the Fourier transform that takes you from the position wave function to the momentum wave function involves an , and .