What is Radioactivity?
- A phenomenon of spontaneous disintegration.
- First observed in certain naturally occurring heavy elements like- radium, actinium, uranium, thorium, etc. with emission of alpha, beta and Gamma rays.
- It is the property of nuclide to disintegrate in which a transformation takes place of a relatively stable nuclide accompanied with the emission of particles or electromagnetic radiation. The nuclide that decay is called radioactive.
- Accidentally discovered in 1896 by French physicist Henry de Becquerel.
- Later Pierre and Madam Curie showed similar phenomenon in other metals like polonium, Francium, and radium.
- Out of all radioactive elements, Radium is the most powerful radioactive element and it was discovered by Madam Curie
- Positively charged Helium atom
- Very little penetrating power
- absorbed by a sheet of paper
- stopped by Aluminium foil
- deflected by electric and magnetic field
- maximum power of ionization through the gases
- velocity is less than that of light
- Negatively charged Light Particle
- stream of fast moving electrons
- Penetrating power is greater than &alpha
- less power of ionization through the gases as compared to &alpha-rays
- Electromagnetic radiation of low wavelength, high frequency and high energy
- penetrating power is very great
- can pass through several centimeter of lead
- composed of photons of high energy
- velocity is equal to the velocity of light in vacuum
Half life period of a radioactive element
- Time during which half of the total number of atoms of the radioactive element disintegrate
- Different radioactive elements have different half lives
- Independent of all external conditions such as temperature, pressure, mass, etc.
- Can be detected by means of its half life period
- Smaller the half life period of a radioactive element, larger is its radioactivity and vice versa.