Radiation principle
Radiation refers to the transmission of energy in the form of waves or subatomic particles. The radiant energy radiates straight from the radiation source in all directions.
Radiation is emitted outward in the form of electromagnetic waves and particles (such as alpha particles, beta particles, etc.). Radio waves and light waves are both electromagnetic waves. Their propagation speed is fast, and the propagation speed in vacuum is the same as that of light waves (3 × 10 ^ 8 m / s).