> What is the amplitude of a single photon's wave? That doesn't have a well-defined answer, unfortunately. Suppose the electromagnetic field contains a single

> What is the amplitude of a single photon's wave? That doesn't have a well-defined answer, unfortunately. Suppose the electromagnetic field contains a single photon. Its electric field then necessarily exists in a superposition of values, so it doesn't have a well-defined amplitude. It also doesn't have a definite "typical" amplitude either -- that depends on how spread out the photon is, and its frequency. As a rough estimate, a photon of frequency omega has energy hbar omega, so if it's spread out over a volume V, then matching energy densities gives E^2 V ~ hbar omega, so you expect the rms value of E to be of order hbar omega / V.