Hi I had some questions about the nature of the spectrum of electromagnetic radiation, as to whether it is continuous or quantifiable, and whether it is infinite or finite. I haven't been able to find satisfactory answers so far and I'm very interested in the knowledge of this forum. Can the difference between the frequency (and therefore the energy) of two different waves of electromagnetic radiation be infinitely small? Can the frequency and energy of electromagnetic waves be measured in natural units of an indivisible quanta? Are there any upper or lower constraints on the frequency or energy an electromagnetic wave can possess? Do any of the answers to these questions change for an individual photon? Thanks for your help.