Radiation
Light, heat radiation, radio waves, X-rays, and radioactive materials are all examples of radiation. There are radioactive substances everywhere, and have been ever since the universe came into existence.
The radioactive substances created by human actions are, therefore, not a new phenomenon in the world. Radioactive isotopes of uranium, thorium, and potassium are found in the natural environment.
What causes radiation?
If the nucleus of an atom has too many or too few neutrons, it is in an excited state. Substances that contain excited nuclei emit radiation. The excited state of the nucleus will disintegrate sooner or later as a particle and a small amount of energy leave the nucleus. This is called radiation.
Radiation that carries enough energy to free electrons from the targeted atoms or to break molecules is called ionizing radiation. Radioactive substances emit ionizing radiation. Devices, such as x-ray machines, can also produce ionizing radiation.
Non-ionizing radiation consists of electromagnetic waves and is utilized in applications such as mobile phones and microwave ovens. The radiation of the Sun is also non-ionizing radiation.