
13Principles of Wave Optics
that location. is subtle distinction emphasizes the point that interference is a single photon phenom-
enon and is not caused by interactions of photons.
Photons interact exclusively with charged particles, most oen with electrons. In fact, almost every-
thing we know about the world is transmitted to us through the photon–electron interaction. For exam-
ple, heat in the sun or a lightbulb excites electrons, which when accelerated emit electromagnetic waves
(photons). e photons either reect o of surfaces or interact with electrons on the surface which
absorbs and reemits photons. Finally, the photons are detecte