Photons are elementary particles that are considered massless according to the Standard Model of particle physics. Despite having no rest mass, photons do possess energy. This is due to their inherent wave-particle duality, where they exhibit both wave-like and particle-like properties.
In the case of photons, their energy is associated with their frequency (or equivalently, their wavelength) according to the equation E = hf, where E represents the energy of the photon, h is Planck's constant (a fundamental constant in quantum mechanics), and f is the frequency of the photon.
The wave-particle duality of photons means that they can exhibit wave-like behavior, such as interference and diffraction, and particle-like behavior, where their energy is quantized in discrete packets called photons. This duality is a fundamental aspect of quantum mechanics.
In the electromagnetic spectrum, photons with higher frequencies (shorter wavelengths) have higher energy, while photons with lower frequencies (longer wavelengths) have lower energy. For example, gamma rays have extremely high frequencies and energies, while radio waves have lower frequencies and energies.
It's important to note that massless particles, like photons, can still carry momentum and energy through their electromagnetic interactions. Although photons have no rest mass, they can transfer their energy and momentum to other particles when interacting with them, such as in processes like absorption, emission, or scattering.