phy - radioactivity

• Radioactivity - it is the random and spontaneous emissions of alpha, beta or gamma radiation from an unstable nucleus.
• Random - can not predict when an atom decays or which atom will decay
• Spontaneous - not influenced by environmental factors
• atoms are unstable due to too many or to few neutrons
• alpha decay - process of emissions of alpha particles from an unstable nucleus
• beta decay - neutron gets converted to a proton and an electron, this electron is emitted as beta
• during gamma emission, energy of the nuclei decreases
• Background Radiation - low level radiation present in the environment around us
• major contributors of background radiation - radon gas, cosmic rays, food and drinks, buildings and soil
• Irradiation - exposure of an object to radiation
• contamination - when an object has acquired some unwanted radioactive substance
• Effects of nuclear radiation/nuclear isotope on cells -

  1. Kills cells
  2. Forms tumors/ Cancer
  3. Genetic mutation
• Kills cells - an intense dose of radiation causes a cell to ionise and kills the cell (Radioactive burn)
• Forms tumors - it can damage the DNA in the cell nucleus and the cell may divide uncontrollably (Cancer)
• Genetic Mutation - if an affected cell is a gamete, the damaged DNA passes on to the future generation, causing genetic mutation.
• Alpha radiation coming from a source outside our body is less dangerous because alpha is entirely absorbed by the layers of dead skin, clothes, etc.
• Alpha source getting inside our body is very damaging because it is highly ionizing, therefore damaging our cells.
• Radon and Thoron gases are dangerous as we breathe them into our lungs, which may lead to lung cancer.
• Half Life -

  1. it is the time taken for half the number of radioactive atoms in a sample to decay.
  2. it is the time taken for the activity of the source to be reduced to half it's original value.
• Activity - No. of decays per second

  unit for activity - Bq (Becquerel)
• Count rate - it is the number of radioactive emissions detected per second

  unit of count rate - counts per second OR Bq
• GM Counter will not detect every emission, therefore activity and count rate are not equal
• N = No/2^n