In the context of photons, which are particles of light, it is important to note that they do not have a well-defined classical wave structure like waves on a string or water waves. Photons are quantum entities and exhibit both particle-like and wave-like characteristics.
The wave-like behavior of a photon is described by its associated wave function, which determines the probability distribution of finding the photon at different positions. The wave function of a photon typically represents a wave packet, which is a localized disturbance that can exhibit characteristics of a wave, such as interference and diffraction.
A single photon can be thought of as a localized disturbance or a "packet" of electromagnetic energy that carries a specific amount of energy and momentum. It does not have a well-defined spatial extent or a specific number of wave crests in the classical sense.
The wave nature of photons is better understood by considering phenomena such as interference and diffraction, which arise from the superposition of multiple possible paths that a photon can take. These phenomena are observed when a large number of photons are considered, and the statistical distribution of their arrival patterns displays wave-like interference patterns.
In summary, a single photon does not have a well-defined number of wave crests, as its wave-like behavior is described by a wave function and exhibits characteristics of a wave packet rather than a classical wave.