1. RADIOACTIVITY THE IDEAS THAT HAVE LIGHTED MY WAY HAVE BEEN KINDNESS, BEAUTY AND TRUTH. ALBERT EINSTEIN Ch3. J.C. Rowe Windsor University School of Medicine

2. Concept Map radioactivity Type of radiation emitted Penetrating powers Used of radioactive substances Half-life

3. Radioactive decay  An unstable nucleus changes by ejecting small fragments. This process is called radioactivity.  The changing radioactive atoms are said to decay.  Fragments which can be thrown out include: 1. Neutron 2. Alpha particles (bundles of 2 neutrons & 2protons) 3. Beta particles (which are electrons) 4. Gamma rays (which are electromagnetic rays like X- rays.

4. Cont’d  The number of protons in the nucleus changes when an atom emits alpha or beta particles.  Losing gamma-rays only reduces the energy of the nucleus.

5. Half-life  Each radioactive isotope decays at its own fixed rate  The time taken by one-half of the atoms to decay is constant  Half-lives can vary from tiny fractions of a second to hundreds or thousands of years

6. Penetrating power  Alpha & beta particles & gamma rays have different powers of penetration. 1. Alpha particles are stopped by a sheet of paper or human skin. 2. Beta particles will penetrate a thin sheet of metal 3. Gamma-rays may penetrate several inches of lead.

7. Cont’d alpha beta gama tissue aluminium lead

8. Uses of radioactivity  Chemical tracer  To date ancient objects  To produce electricity on a large scale & small scale  In radiotherapy  In smoke alarms  To sterilize materials

9. The future belongs to those who believe in the beauty of their dreams. Eleanor Roosevelt