We already know that gamma radiation is high-energy electromagnetic radiation. But what does that mean exactly and what consequences does it have for measuring radiation?
Let's take a closer look at the term of electromagnetic radiation. We start with a definition:
Electromagnetic radiation refers to the propagation of energy in the form of waves or particles.
This definition may seem a bit unclear at first glance. But just look around: The sunlight that might be shining through your window, or the lamp on your ceiling, the music that your DVD player or digital radio plays, the microwave that heats your food, the radiator warming your room, the tanning bed you can grill under, etc. All these things and many more in our daily lives are sources of radiation. The radiation differs only in its energy. The following graphic provides an overview of the different designations for the individual areas of the electromagnetic spectrum. The energy of radiation decreases from left to right.
Schematic representation of the electromagnetic spectrum (by Horst Frank / Phrood / Anony - Horst Frank, Jailbird and Phrood, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3726606)
Further information:
If you have examined the illustration closely, you may have noticed that the three horizontal axes below the designations of the sources indicate the corresponding wavelength in meters (m), the corresponding frequency in hertz (Hz), and the energy in electronvolts (eV). This shows that the different units can be "converted" into each other. For example, frequency is directly proportional to energy. This means that to find the corresponding value for the energy of radiation, you simply have to multiply the frequency value by a constant number (we will discuss exponential notation of numbers, the units, etc. in the Advanced section).
The definition also states that electromagnetic radiation propagates like waves or particles. In our everyday lives, we actually always experience electromagnetic radiation behaving like waves. No wonder we talk about microwaves, optical fibers, etc. But why do we still have the term particles in the definition? Well, that has to do with the famous phenomenon known as wave-particle duality. The results of some experiments can be better explained when electromagnetic radiation is described in terms of waves, while others can be explained better when described in terms of particles. This strange behavior that radiation sometimes behaves like waves and other times like particles can only be explained through quantum physics.
Meme about the famous double-slit experiment in quantum physics. Radiation behaves as waves when passing through a double-slit (top) and as particles when going through it (bottom).
After this brief excursion into one of the "strangest" areas of physics, we now return to our original question of how to measure electromagnetic radiation.
It is helpful to introduce the terms ionizing radiation and non-ionizing radiation.
However, we need to clarify our description of the atom a bit further. Among the two types of particles in the nucleus, protons and neutrons, each proton has a positive charge, while all neutrons are uncharged. Each electron in the atomic shell, on the other hand, has a negative charge. If an atom consists of equal numbers of protons and electrons, it appears uncharged externally and is electrically neutral.
Model of an atom; inside: nucleus with protons (p) and neutrons (n); outside: electrons (e) (Source: https://commons.wikimedia.org/wiki/File:Atom_animation.gif)
But what does this have to do with radiation? Quite simply! If radiation has enough energy upon striking or approaching the atom, it can dislodge individual electrons from the atomic shell. The atom then lacks electrons after this process. It has become a positively charged ion. This type of radiation is consequently referred to as ionizing.
