What is radiation How is it generated?


There are different types of ionizing radiation:

Alpha radiation is particle radiation whose individual particles consist of two protons and two neutrons. An alpha particle is therefore a nucleus of the nuclide helium-4. Alpha particles are slowed down very strongly by matter (e.g. air or water) and therefore only have a very short range (a few centimeters in air; less than a millimeter in water). They can already be shielded by a sheet of paper.

When exposed to the outside world, alpha radiation can only penetrate the outer layers of the human skin. If alpha emitters - i.e. radioactive substances that release alpha particles when they decay - enter the body via the air we breathe or the food (incorporation), this can lead to considerable radiation exposure. Since the alpha particles emit their energy over a very short distance, they damage the tissue particularly severely.

A typical and important example of the incorporation of alpha emitters is the absorption of the naturally occurring noble gas radon and its secondary products with the air we breathe.

Beta radiation is particle radiation that occurs when radioactive atomic nuclei emit (negatively charged) electrons or, less often, positrons (particles that have the same mass as electrons but are positively charged) when they decay. Beta radiation is less strongly absorbed by matter than alpha radiation and therefore has a greater range. The penetration capacity of beta particles is a few centimeters to meters in air and a few millimeters to centimeters in soft tissue or plastic. Beta radiation can be shielded relatively easily, for example with an aluminum sheet that is a few millimeters thick.

Radioactive particles that emit beta radiation can also lead to considerable radiation exposure if they are absorbed (incorporated) into the body with the air we breathe or with food. Beta radiation, which acts on the body from outside, can also damage the tissue because it can penetrate the body, albeit not very deeply. However, it emits significantly less energy per distance than alpha radiation. It is said that beta radiation has a lower biological effectiveness than alpha radiation.

With gamma radiation, energy is transported as an electromagnetic wave. The electromagnetic radiation can be described in terms of its frequency or its wavelength. The higher the frequency and the shorter the wavelength, the more energetic the radiation. Gamma radiation is at the high-energy end of the "electromagnetic spectrum", at a high frequency or a short wavelength.

Gamma radiation occurs when radioactive atomic nuclei decay, often in addition to alpha or beta radiation. It penetrates matter very easily. Heavy materials such as lead and concrete are used for shielding.

Gamma radiation is harmful to living beings, both when exposed to the outside and when incorporated, since it penetrates deep into the tissue. However, their biological effectiveness is lower than that of alpha radiation, for example, as it emits less energy to the tissue over a certain distance.

X-rays are also electromagnetic radiation. In contrast to gamma radiation, it is technically generated when fast electrons are slowed down at the anode (positively charged electrode) of an X-ray tube.

The higher the applied tube voltage, with which the electrons are accelerated in the X-ray tube, the shorter-wave and therefore more energetic the resulting X-ray radiation. When the X-ray tube is switched off, no X-ray radiation is generated.

Neutron radiation consists of uncharged particles (the neutrons). Neutrons are particularly released during nuclear fission.

Neutron radiation is hardly absorbed by air. Materials with the highest possible hydrogen content (for example paraffin, polyethylene, water) are used to initially slow down the neutrons. The decelerated (thermal) neutrons must be captured by an absorber (for example boron or cadmium). The gamma radiation released at the same time must be shielded with lead.

Mainly due to the strong interaction with biological tissue (especially the water molecules it contains), neutron radiation has a high biological effectiveness.

Jump to the top of the page Jump to the content of the page