Question

If photons are the excitation of a field rather than a particle, do they actually propagate omnidirectionally like a sound wave until “observed”?

Answer 1

The behavior of photons can be understood through the framework of quantum mechanics. According to this theory, photons are elementary particles and quanta of electromagnetic radiation. While they do exhibit wave-particle duality, it is important to clarify a few aspects related to their propagation and observation:

1. Photons as Excitations of a Field: In quantum field theory, particles are considered as excitations of underlying fields. The electromagnetic field is associated with the existence of photons. Photons are the quanta of energy that propagate through this field when electromagnetic waves are generated.

2. Propagation of Photons: Photons can propagate in space as electromagnetic waves in all directions. When a light source emits photons, they spread out in a manner analogous to the propagation of waves, forming a spherical wavefront. This behavior is similar to how sound waves spread out in all directions from a sound source.

3. Observation of Photons: The act of "observation" in quantum mechanics refers to an interaction between the photon and a measuring apparatus or detector. This interaction leads to the collapse of the photon's quantum wavefunction, resulting in a particular outcome, such as detection at a specific location. The process of observation affects the probability distribution of where the photon is likely to be detected.

4. Quantum Superposition and Interference: Before observation or measurement, photons can exist in a superposition of states, simultaneously exhibiting wave-like properties. This superposition allows photons to interfere with each other, leading to phenomena such as diffraction and interference patterns. These interference effects can be observed even when photons are not detected individually.

It is important to note that the concept of "observation" does not require conscious observation by a human or any specific type of observer. In quantum mechanics, it refers to any interaction that disturbs the quantum system being observed.

In summary, photons propagate as electromagnetic waves in all directions until they interact with a detecting apparatus or are absorbed by a material. The wave-particle duality of photons allows them to exhibit both wave-like and particle-like behavior, but their propagation is not dependent on conscious observation.