Hello, I am at present reading about black-body radiation and the derivation of the Rayleigh-Jeans law. I have a few queries, and am hoping they can be answered somewhat simply. What exactly is the mode of an oscillation? Why do the waves in the box have to be standing, and what exactly are standing waves? Why do the waves have to be zero at the boundaries of the black-body cavity, and what does that mean for the waves to be zero at the boundaries?