Fotonai

Fotonai, or photons in English, are the elementary particles that constitute light and other forms of electromagnetic radiation. They are the quanta of the electromagnetic field and act as the force carriers of the electromagnetic interaction. Photons are massless, have spin 1, and exhibit two helicity states in free space. They propagate at the speed of light in vacuum, and their energy and momentum are determined by their frequency or wavelength: E = h f = h c / λ and p = E/c = h / λ, where h is Planck’s constant.

Photons display wave–particle duality: they can interfere and diffract like waves, yet are detected as discrete quanta in detectors. They can be created and destroyed in processes such as emission by excited atoms, spontaneous and stimulated emission, and absorption by matter. Their interactions with matter depend on energy, giving rise to phenomena such as reflection, refraction, scattering, and absorption. In quantum electrodynamics, photons mediate electromagnetic forces and couple to charged particles.

Photons are generated by a variety of sources, including thermal radiation, electrical discharges, electronic transitions in atoms and molecules, lasers, and other light emitters. They are detected with photodetectors, cameras, photomultipliers, and superconducting devices. The properties of photons underpin technologies such as fiber-optic communications, solar energy, medical imaging, spectroscopy, and various imaging and sensing applications. In astronomy and cosmology, photons carry information across space, from starlight to the cosmic microwave background.