Photons are indeed often described as both particles and waves, which is a fundamental characteristic of quantum mechanics. This duality is known as wave-particle duality. While the concept may seem counterintuitive from a classical perspective, it arises from the wave-like behavior of photons and other quantum particles.
In quantum mechanics, particles such as photons are described by wave functions that determine the probability of finding the particle in a particular state or location. These wave functions exhibit wave-like properties, such as interference and diffraction, similar to other waves like water waves or sound waves. This wave nature is evident in phenomena like the double-slit experiment, where photons can exhibit interference patterns like waves do.
On the other hand, particles like photons also exhibit particle-like behavior. They have discrete energy levels and can transfer energy and momentum in quantized amounts. When photons interact with matter, they can be absorbed or emitted as discrete packets of energy. These packets are often referred to as "quanta" or "photons" and can be thought of as particles. The energy of a photon is directly proportional to its frequency, as described by the equation E = hf, where E is energy, h is Planck's constant, and f is the frequency of the photon.
So, while photons are often referred to as particles, it's important to understand that this particle behavior emerges from their quantum nature and their wave-particle duality. The description of photons as particles or waves depends on the experimental context and the properties being observed. In reality, photons and other quantum particles exist in a superposition of both wave-like and particle-like states, and their behavior can be described mathematically using quantum mechanics.