The nuclei of the atoms in some elements are unstable and emit radiation. The radiation can be of three types - alpha radiation, beta radiation and gamma radiation.

All types of radiation become less intense as they travel further away from the radioactive material. This is because the particles or rays become more spread out. The thicker the substance ...

When using solar radiation instruments, the "surface" being discussed is typically the surface of the Earth or a solar panel. The irradiance of a beam of monochromatic light can be manually calculated ...