Radiation

Examples of radiation

Examples of radiation and associated energy include:

How does radiation occur?

For radiation to happen, an atom needs to receive an excess of energy. The energy received alters the particles and makes the atom release radiation. The steps for radiation to occur when releasing a photon are as follows:

1. The atom is in a non-stable state because it has an excess of energy. This excess is caused by a photon carrying electromagnetic energy, which impacts an electron.
2. The non-stable state is also called an ‘excited’ state. Atoms will always seek balance by releasing any excess energy, in this case, the electron will seek to release the energy excess.
3. Excess energy will be released as electromagnetic waves (photons). The energy of the photon released will be linked to the orbit of the electron that was excited.
4. The radiation emitted in the form of photons is an electromagnetic wave and its frequency will be linked to the energy released. Larger energies released will correspond to larger frequencies.

Atoms also release radiation in the form of particles such as neutrons, alpha particles, and beta particles. The process in which radiation is released is known as radioactive decay. In this case, the forces that keep the atom together are out of balance, and the atom releases particles seeking stability. The kinetic energy of the particles is linked to their energy.

How does radiation work?

Radiation is a form of energy – a wave or particle with a charge moving at a certain speed. As a form of energy, it can inject energy into an atom, break it, or move its particles. Radiation can also come from a non-stable atom, as in the following examples:

There are several types of radiation, several radiation sources, and also many uses of radiation.

Classification of the radiation by electromagnetic waves

Radiation by electromagnetic waves can be classified in several ways by considering its wavelength, energy, or source.

One characteristic of radiation is its wavelength. Shorter wavelengths contain more energy, while longer wavelengths have less. Radiation by electromagnetic waves has different names, depending on its wavelength, as can be seen in the illustration below.

Radiation can be ionising or non-ionising. This depends on the amount of energy the radiation has.

• Ionising: if the radiation can change the atomic structure by moving electrons or particles out of the atom, it is called ionising radiation.
• Non-ionising: if the radiation cannot change the atomic structure but can make electrons move their positions up and down, it is known as non-ionising radiation.

Radio waves are an example of non-ionising radiation, while UV radiation from the sun and x-rays are both types of ionising radiation.

Radiation is also classified into waves or particles, depending on the element that carries the energy.

• Waves: these belong to the electromagnetic spectrum and range from radio waves to visible light to highly energetic gamma rays produced by faraway stars.
• Particles: the other source of radiation is particles, which are knocked out from atoms by other particles. This form of radiation consists of electrons, neutrons, and protons that fly off at high velocities.

Sources of radiation

Radiation can come from natural sources or artificial sources created by technological applications.

Natural sources include radiation that reaches the earth from the sun and stars and radiation released by the natural disintegration of atoms in the earth’s crust or even living beings.

Artificial sources include radar systems, microwaves, sources of lighting, heating devices (heat radiation), TV sets, wireless internet and telecommunication devices (including mobile phones), many artificially created short-lived isotopes used in medicine, and many other sources.

Unstable nuclei and atom disintegration

Atomic nuclei are a source of radiation, which occurs when an atom breaks. For an atom to break, it must be unstable, and when it does break, it usually becomes a lighter and more stable element.

Some elements have high stability and can remain the same for billions of years. Others only last a few seconds.

Uses of radiation

Radiation has many uses, including medicine, communications, sterilisation, energy production, and others.

• Medicine: radiation therapy involves the use of focused doses of radiation to kill tumour cells in patients.
• Aviation: radars use electromagnetic radiation to detect aeroplanes. The radar helps to track, detect, and direct the air traffic over any given territory.
• Microwaves: these use radiation to induce vibration on the water molecules. The more they move, the more heat they produce.
• Medical screening tests: MRI scans use radio waves to produce detailed images of the structures inside the human body. CT scans and x-rays use the same principle, but their photons have higher energy.
• Energy: radiation is used in fission reactors to produce energy.
• Communication: mobile phone and satellite communications use radio waves to transmit data.
• Sterilisation: radiation is used in several industries to kill germs and insects.