>[!summary] Particle in a box is a hypothetical situation composed of a left and right moving wave. To describe that momentum is not definite, so that position is also not definite. # Particle In a Box In the [[Single Slit Experiment]] (and [[Double Slit Experiment]]) we saw that $F = ma$ failed A particle in a box is a hypothetical distribution for quantum wave functions. A particle in a box is described as a wave with some wavelength ($\lambda = \frac{h}{p}$) ![[pair_1.png]] [^1] >[!note] Explanation A wave function composed a left and right moving wave in a closed box. The only way to confine a particle in a box is to allow it to be standing wave. We want the probability if the particle to end up at the end of the box or outside the box to be zero. The right moving wave becomes the source of the left moving wave. The left moving wave becomes the source of the right moving wave. They have +p **and** -p simultaneously Particle trajectory is not definite because the momentum is not definite (its not -p or +p anymore) [^1]: Taken from R.Epp notes.