The right answer is Radiation.
Radiation, refers to the process of emission or propagation of energy and momentum involving a wave, a particle.
Solar radiation is the set of electromagnetic waves emitted by the Sun.
It is made up of the full range of radiation, from far ultraviolet like gamma rays to radio waves and visible light. Solar radiation also contains cosmic rays of moving particles of extremely high speed and energy.
Sunlight is necessary for human health:
* the day-night cycle holds most human biological cycles;
* Solar UV is necessary for the synthesis of vitamin D;
* Solar UV also contributes to the destruction of some living or surviving microbes or those that have contaminated bathing waters or waters that can be used as drinking water or irrigation, with less efficiency in turbid waters, or made turbid by human activities.
