just over a century ago was considered the smallest atom of naturally occurring particles unchanged and indivisible.But scientific thought did not stand still, restless human mind sought more to lift the veil of secrecy over the properties of the elements.And now, at the end of the XIX century French physicist Becquerel, conducting research of X-rays, accidentally became interested in the radiation emitted by uranium salts.So in 1896 was the discovery of radioactivity - this is the most obvious evidence of the divisibility of the atom.
scientific community was greatly interested the opening, and a galaxy of talented physicists devoted herself to study it.As it turned out, often bringing to the altar of the health sciences.Thanks to them, we now know that the radioactivity - a phenomenon spontaneous spontaneous emission of particles of different nuclei of some elements, in which the nucleus eventually move to a different state and change their settings.
atoms of radioactive substances emit particles and electromagnetic radiation.Among them are the following:
- alpha particles (α) is a stream of completely ionized helium atoms, moving at a speed of 20 thousand. Km / s and have the ability to penetrate into the air at a distance of 10 cm. Hold these particles from entering the human bodycan clothes, paper, leather.But penetrating into the body, they cause significant harm;
- beta particles (β) - is a fast electrons (or positrons), which has a flow rate close to the speed of light.Their penetration ability in the air is much higher - up to 5 - 20 m. And let them be able sheet of aluminum a few millimeters thick;
- gamma rays (γ) - occurs when nuclear interactions and transformations of particles electromagnetic radiation with a very short wavelength.Penetration of this type of radiation is so high that it can only hold a thick sheet of lead or concrete layer.When
number of spontaneous nuclear reactions is emitted neutral particles - neutrons penetrating power which is higher which have γ-rays - they pass through the lead-up to several meters thick.
known that radioactivity - a property that may be inherent in the elements of nature, and can be achieved by a laboratory.The artificial radioactivity was discovered in the 30s of XX century.
sources of natural radiation are many.This is the planet Earth itself, and space, and nuclear power plants with their waste, and chemical elements in soils and building materials, and a number of household items.But this people try not to think.
There are several devices measuring radioactivity units are also different.The basic unit - becquerel (Bq), equal to one disintegration per second.Common Units are used: X-ray, curies.Absorbed dose is measured in units rad or gray.Effects on biological organisms evaluated in rem or sievert.
natural radioactive materials emit particles bombarding us throughout life.One of the sources of radiation constantly perform artificial structures - residential and commercial.Even a number of natural materials has somewhat elevated background radiation.For example, the natural radioactivity of granite makes buildings more than doubled from a radioactive (400 mrem / year) than the built of red brick, four times - the concrete.Least of all the charged particles emits tree - building of a 13 times less radioactive than granite.
The benefits to humanity radioactivity - is undeniable fact.Science, medicine, agriculture, energy, and many industries are hardly treated to no radioactive isotopes.But when the peaceful atom becomes uncontrolled or transformed into a weapon, he is a threat to the existence of our planet.