Radioactivity

4.7 Cathode-ray oscilloscopes

5.2 The nuclear atom

Radioactivity

  1. Characteristics

    1. Radioactive emissions occur randomly over space and time

    2. Characteristics of the three kinds of emission:

      Emission Nature Relative ionising effects Relative penetrating abilities Deflection in electric fields
      Alpha particles High-energy helium nuclei High Low Towards negative
      Beta particles High-energy, high-speed electrons Medium Medium Towards positive
      Gamma rays Electromagnetic radiation of extremely high frequency
      High-energy photons      		 Low High None

  2. Safety precautions

    1. Sources should be kept in lead-lined containers to prevent radioactive leakage whilst in storage
    2. Radioactive sources should be kept away from the body, especially the eyes, and handled to tongs
    3. Exposure to radioactive sources should be limited and from as far a distance as possible

  3. Detection

    1. Radioactive particles can be measured using a Geiger counter, which counts the number of ionising events detected by a Geiger–Müller tube, which detects radioactive particles ionising an inert gas in it by passing a strong electric field through the gas that amplifies the signal of the radiation into an easily-measured pulse. When measuring levels of radioactivity, the base level of background radiation must be accounted for by being subtracted from the measurements

  4. Radioactive decay

    1. Radioactive decay is the process by which the nucleus of an unstable atom spontaneously decomposes, emitting particles of ionising radiation
    2. The half-life of a radioactive substance is the amount of time required probabilistically, for half of the atoms to undergo radioactive decay