What is Radioactivity?

The term radioactivity is used in reference to express the behavior or property of some specific material matter that exhibits spontaneous emission of energy or subatomic particles. It is sometimes called radioactive decay.

One should note here that any molecule that has an unstable nucleus will decompose into one or more stable units and during the same, some particles or electromagnetic energy will be emitted.

Basics of Radioactivity

Radioactivity is a natural phenomenon. We have already mentioned in the beginning that in this process, energy or radiation is emitted from the atomic nucleus.

Basically, radiation can be of alpha, beta, or gamma types. However, if we talk about nuclear radiation then in that case emission of protons or neutrons also takes place. Radioactivity is noticed in numerous substances.

One should note here that various natural materials on earth exhibit radioactivity by emitting invisible, energetic radiations. The emitted radiations cause harmful effects on the cells present in the living bodies however, these radiations also show crucial applications in the field of medicine when used carefully.

The emitted radiations are impossible to get detected by the five senses of the living body and hence the phenomenon was detected after the invention of radiation detectors.

Invention of Radioactivity

Radioactivity was invented in Paris in the year 1896 by French physicist Henri Becquerel. Becquerel’s father was a Professor of Physics who was investigating the phenomenon of phosphorescence.
This phenomenon was assisted by Becquerel which was associated with some substances emitting visible radiations when exposed to a source of bright light. He also experimented that when crystals of uranium and potassium are exposed to sunlight then they eventually glow. However, when taken into the dark the crystals stop glowing.

Becquerel in 1896 heard Henri Poincare in a lecture on the discovery of X-rays by Wilhelm Rontgen. In his lecture, Poincare explained that when the electron beam is accelerated then the spot where the beam strikes the glass, visible light gets emitted. This is nowadays called fluorescence.
During the experiment, it was also observed that from the same spot unknown invisible radiation also gets emitted. The invisible radiation was coined as X-ray where X is used to refer to the unknown radiation.

It was observed that X-rays are the type of radiation that has the ability to penetrate solid regions and cast shadows on a photographic surface.

With this experimental analysis, Becquerel concluded that X-rays and phosphorescence are interrelated and so he wanted to check whether x-rays can also be emitted from the phosphorescent crystals. For the same various experiments were conducted.

Becquerel in his experiment tightly covered a photographic plate with a light paper and placed phosphorescent crystals over it. The whole arrangement was exposed to the sun for some hours so that sunlight can act as the source of energy.
During observation, it was noticed that the surface gets blackened where crystals were present. Also, the presence of any metallic plate in between thin paper and crystals will lead to casting shadows. Hence his experiment confirmed that x-rays are part of phosphorescence.

Becquerel wanted to continue his experiment but there were poor weather conditions. Accidently he placed crystals over a wrapped photographic plate inside a drawer. When he opened the drawer after some days, he surprisingly saw that an equivalently intense image has been produced on the plate, like the one which gets produced when exposed to sunlight.
By this, he concluded that the crystals have the ability to blacken the surface even in the absence of sunlight.

Hence, he concluded that invisible radiation gets emitted even in the presence of sunlight which was a completely different experiment.

Later some other scientists took part in the experimental analysis in their own way. Marie Curie was one of them who suggested the term radioactivity for this phenomenon. She explained that radioactivity is a property of atoms and so cannot be varied through physical or chemical processes.

Types of Radioactivity

The various types of radioactivity are as follows:

Alpha Radioactivity: When helium nuclei having two protons and two neutrons (i.e., two positive charges) are emitted then alpha radiation is emitted. Those atoms which contain various protons and neutrons are said to emit alpha radiation. When radioactivity takes place then a different chemical element with a lighter nucleus will be produced.

Beta Radioactivity: These are classified into two categories.

  • Beta minus radioactivity: This type of radioactive decay is associated with negatively charged electrons. When atomic nuclei that have a large number of neutrons are disintegrated into proton plus electron then the electron will get ejected and a different chemical element is produced.
  • Beta plus radioactivity: This radioactive decay is associated with positrons. Atomic nuclei that contain a high amount of protons emit beta plus radiation. Here in this case positron is emitted and a new chemical element is produced.

In both beta minus and beta plus radioactivity, the nucleus has the same number of nucleons.

Gamma Radioactivity: Gamma radiation is a highly energetic electromagnetic radiation. This radioactivity can be followed by alpha or beta decay. Basically, when alpha or beta particles are emitted then because of the non-equilibrium of protons and neutrons the nucleus exists in the excited state. Therefore, the excess energy gets released when gamma radiation is emitted.

Applications of Radioactivity

Some of the major applications of radioactivity are as follows:

1. In medicine: Radioactivity is extensively used in diagnosing and therapy-related applications. This has cleared the paths for the field termed nuclear medicine. The radioisotopes are very much useful in tracing during some diagnostic processes. Radioactivity helps in tracing radioisotopes in certain minutes.

2. In study of the environment: When the absorption rate of the emitted radiation is determined then one can find the density of the medium through which the radiation is traveling. Hence by this, we can monitor the suspended matter within the water of rivers, lakes, etc. Along with that, sediments of pollutants can also be tracked. This also helps in determining the pollution level.

3. In industry: This finds applications in the field of power generation where nuclear fission takes place. Other than this, radioisotopes are used in measuring the thickness and density of sheets of metals or plastics. This also helps in analyzing how effective motor oil is.

4. In science: Research-related applications also make use of radioisotopes where it is studied the decay of geological material. With this technique, one can study rocks and rock formation.

This is all about radioactivity.

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