It is by observing spectral lines, both in emission and absorption that we are able to determine the chemical composition of stars and galaxies in our universe. Chapter 30 Light Quanta Ok, so now we have shown without any doubt that light is a wave phenomena. This would tend to totally discredit the ideas of Newton who thought that light was some sort of particle phenomena. Classically speaking, which means speaking from everyday experience, waves are waves and particles are particles. However, let us investigate just what properties waves and particles actually have.
Particles have mass, but mass is energy.
Now you have to do work to set up a wave in any medium. But waves are always in motion at the wave speed of the wave in the medium the wave is traveling in. Now the distinction is obvious at the level of the macroscopic world in which we live, Particles are like balls and rocks and waves are like the waves on a piano string of in the ocean. They clearly appear to be different phenomena in our world. But since theory says they are basically indistinguishable at a fundamental level, we need to ask the question could there be a small scale at which in fact particles and waves are all the same sort of phenomena.