Radiation is the emission, propagation and transference of energy through any medium, in the form of electromagnetic waves or particles.
An electromagnetic wave is a way to transport energy (for example, the heat transmitted by the light of the Sun).
Classification of electromagnetic radiations
Electromagnetic waves or radiations can be classified into:
- Non ionizing radiation: They lack enough energy to break the links that hold together the atoms of the medium they irradiate (radio waves and TV, microwaves, visible light, etcetera).
- Ionizing radiation: They have enough energy to produce ionizations of the atoms in the irradiated medium or matter. They range from X-rays to cosmic radiation.
Classification of ionizing radiations
Radioactivity is a physical phenomenon whereby some chemical elements or bodies known as radioactive emit radiations that have the property of exposing photographic plates, ionizing gasses, producing fluorescence, etcetera.
It is one of the great discoveries of contemporary man. Along with its effects greatly useful applications were discovered, since radioactive substances or ionizing radioactivity emitting instruments are irreplaceable in medicine, agriculture, industry, Earth sciences, biology and many other fields.
The emission of ionizing radiations is a common characteristic for many atoms in whose nucleus the number of neutrons is scarce or excessive, which makes them stable (radioactive). This leads to the transformation of their nuclear links as they seek more stable configurations, at the same time liberating energy associated to the emitted radiation.
Types of radiations
According to their interaction with matter:
- Alpha: With limited capacity to penetrate matter but high energy density.
- Beta: Somewhat more penetrating, but less intense than alpha radiations.
- Gamma: The most penetrating radiation of all.
Origin of radiations
People are continually exposed to ionizing radiations. Some of these radiations come from nature, without any human interaction in their production, and others are originated by human actions.
On average, the dose derived from natural radiation received by a person in Spain is around 2.4 mSv/year
Natural radioactivity can be derived from three different causes:
- Outer space (cosmic radiation): These radiations reach Earth every second (protons (86%) and alpha particles (12%)). Since the atmosphere partially absorbs radiations, the natural base due to this cause varies according to altitude, in such a way that it is less below sea level than atop a mountain. To the world average, cosmic radiation amounts to 10% of the dose.
- The Earth’s crust: 14% of the world’s average dose.
- Human organism: Mainly carbon and potassium isotopes, contributing to approximately 52% of the world’s average dose.
On average, the dose derived from natural radiation received by a person in Spain is around 2.4 mSv/year.
They are the result of exposition to diverse non natural sources, such as: radiological explorations with medical purposes (the majority of sources, they deliver doses to the population similar to those of cosmic radiation), air travel (in this case, the greatest cosmic radiation doses received are in high-altitude flights), etcetera.
Factors that determine a higher or lower radiation dose
The radiation dose received by an individual located near a radiation source depends on three factors:
- The distance between the radiation and the individual: the dose received proportionally decreases as the distance between the individual and the source increases.
- The Time of permanence: the dose received increases in proportion to the time of exposition to radiation.
- The Shielding between the radiation source and the individual: Shielding reduces exposition to ionizing radiations in persons who are near to a radiation source.
Sources and effects of radiation doses
|Average exposition in a year
|New York – London flight
|Mamography (two visits)
|260 (above sea level)
400 (1,000 m above sea level)
650 (2,000 m above sea level)
|Food and water
|400 (natural origin)
|Computer screen (8h/day)
|Airplane flight (10,000 m high)
Radiation doses (mSv) and their effects
|Dose limit by law
|Dose value that could entail risk cáncer
|Dose value that could cause serious illness
|Dose value that could casue death within a month