lichtquanta

Lichtquanta, or light quanta, are the quantum units of the electromagnetic field. In modern physics these quanta are called photons: massless, spin-1 bosons that carry energy and momentum. The energy of a single lichtquanta is proportional to its frequency, E = h f, and its momentum is p = E/c = h/λ, where h is Planck's constant and λ is wavelength. Photons obey quantum rules and interact with matter in discrete amounts.

Historically, the concept arose to explain the photoelectric effect and black-body radiation. In 1905 Albert Einstein proposed that light of frequency f is quantized in units of Lichtquanta, helping to account for the emission and absorption of energy by electrons in atoms. This complemented the wave description of light and established the particle aspect of light.

In practice, the number of quanta relates to light intensity: higher intensity corresponds to more quanta per unit time, while the energy per quantum depends on frequency. Interactions with matter occur via absorption or emission of individual quanta; transitions between atomic energy levels require matching hf. Experimental evidence includes photoelectric measurements, Compton scattering, and black-body radiation experiments, all supporting the photon model.

Today, Lichtquanta are fundamental in quantum electrodynamics and underlie technologies such as lasers, LEDs, solar cells, and many spectroscopic techniques. The term lichtquanta is the German designation for photons; in English, the standard terms are photon or light quantum.