Radiation
Radiation is all around us all the time. It comes from space, from radioactive substances in the ground and in what we eat.
Different types of radiation
There are different types of radiation with different properties. For example, there is ionizing radiation and non-ionizing radiation, which in turn can be divided into optical radiation and radio frequency radiation.
Ionizing radiation
Ionizing radiation can be divided into electromagnetic radiation, a wave motion of electric and magnetic fields (gamma rays and X-rays) and particle radiation, a stream of particles from atomic nuclei (alpha, beta and neutron radiation). Gamma rays and X-rays are the same type of radiation, but with different origins. X-rays are artificially created using X-ray tubes, gamma rays come from the atomic nuclei of radioactive substances.
Ionizing radiation can form ions in the irradiated object, known as ionization. Ionization can cause permanent changes or damage to the irradiated object, for example to the genetic material in the body's cells. A common misconception is that what is irradiated also becomes radiant. However, objects that are contaminated with radioactive particles can become radiant.
Alpha radiation has a short range and is stopped by a piece of paper or a thin layer of skin. Beta radiation passes through the paper but is blocked by a centimeter-thick Plexiglas sheet. Gamma radiation can be reduced to half by either 1 cm of lead, 5 cm of concrete or 10 cm of water.
Non-ionizing radiation
Non-ionizing radiation is electromagnetic radiation that cannot break atoms or molecules. It also does not produce ions, but this does not prevent it from causing other changes and damage to the object being irradiated. For example, ultraviolet radiation (UV radiation) can cause sunburn and, in the worst case, change the properties of skin cells in a way that can lead to cancer.
Non-ionizing radiation is divided into optical radiation and radiofrequency radiation. Optical radiation is in turn divided into visible light, UV radiation and infrared radiation. The part of optical radiation that we can perceive with our eyes is visible light.
UV radiation comes mostly from the sun, a natural source of radiation that can also be artificially created (in tanning beds and electric welders, for example). Infrared radiation is emitted from all hot objects, such as light bulbs and stove tops. Radiofrequency radiation includes microwaves and radio waves, as well as low-frequency electromagnetic fields, most of which are man-made. Ultrasound is also considered non-ionizing radiation and is man-made.
Over the last century, humans have developed ways to create and use radiation in research, healthcare and industry, for example by using X-ray technology and by using uranium in nuclear reactors.