What is meant by electromagnetic

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If energy spreads in a directed, temporal and spatial manner, one speaks of radiation. The energy can be transported through particles (particle, corpuscle, particle radiation). This is the case with alpha radiation, which consists of high-energy helium nuclei (Fig. 1). If the radiation particles have mass, charge or other properties, these are also transported. However, energy can also propagate in the form of waves (wave radiation), as in the case of sound, in which density fluctuations are propagated through matter (Fig. 2).

The historical debate as to whether light rays consist of particles or waves was answered as follows in quantum theory: They consist of photons (particles) that show wave properties (e.g. interference). In general, one can justify from quantum physics that all radiations must have both particle and wave character. This is known as wave-particle dualism.

Radiation is a directed, temporal and spatial energy transport in the form of waves and / or particles. Radiation always transports energy and momentum (i.e. it has an excellent direction).

The term beam is rather fuzzy and not strictly defined. So there is a jet of water, but no water jet. On the other hand, there is both a ray of light and a ray of light. When one speaks of matter that spreads like rays, what is meant is a flow of particles or matter, not radiation of matter.