Whispering gallery modes or waves are specific resonances or (eigen-)modes of a wave field (e.g. sound waves,electromagnetic waves, …) inside a given resonator (a cavity) with smooth edges. They correspond to waves circling around the cavity, supported by continuous total internal reflection off the cavity surface, that meet the resonance condition (after
one roundtrip they return to the same point with the same phase (modulo ) and hence interfere constructively with themselves, forming standing waves). These resonances depend greatly on the geometry of the resonator cavity.)