What is radiation? Electromagnetic & Particulate radiations [with exercise questions]

What is Radiation?

In physics, radiation is defined as energy that travels through space or matter in the form of a particle or wave. It can be produced in one of two ways: by radioactive decay of an unstable atom (radionuclide), or by the interaction of a particle with matter. Some attributes of radioactive decay are spontaneousness and randomness. The type of radiation emitted depend on the specific radionuclide. Radiation emission as the result of an interaction depends on both the incoming particle and the material it hits, and is theoretically predictable if enough information is known.

Electromagnetic & Particulate Radiations

Radiation is described by its type and energy. The types of radiation fall into two main categories: particulate and electromagnetic.

• electromagnetic radiation consists of photons that have energy, but no mass or charge, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ). A photon, as described by quantum theory, is a “particle” or “quantum” that contains a discrete quantity of electromagnetic energy which travels at a speed of light.
• particulate radiation consists of particles that have mass and energy, and may or may not have an electric charge, such as alpha radiation (α), beta radiation (β),proton radiation and neutron radiation.

Those radiation type above will be discussed in next section in detail. The most common unit of energy used to describe radiation is the electronvolt(eV). An electronvolt is the amount of kinetic energy an electron gains when accelerated through a potential difference of one volt. The conversion to SI units is $1eV = 1.6*10^{-19}$ Joules.

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