I've heard that basically photons can exhibit wave-like or particle-like based on what kind of experiment you perform to prove one or the other. However, are they hence both waves and particles at the same time? I'm not sure if this is a proper question, or if I'm misunderstanding something, but I'm basing this on the fact that when exciting atoms such as the hydrogen atom, it will produce a spectrum of light. If an atom can produce a spectrum of light, then that light would have to be wave-like, right? Otherwise, it would be matter, and hence if you were to continue exciting the particle and it were to continue releasing the light from that spectrum, then shouldn't it eventually (after a long time) lose all it's mass to the photon? Thanks for any enlightenment anyone can offer me! Edit: Mistyped Photon as Proton. Thanks, Berkeman!