Properties of Radiation

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  • Created by: gracedean
  • Created on: 30-03-15 14:06
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  • Properties of Radiation
    • Nuclear Radiation
      • There are three main types of ionising radiation emitted from the unstable  nuclei of radioactive atoms - these are alpha, beta and gamma radiation.
        • Alpha radiation  consists of alpha particles. An alpha particle is identical to the nucleus of a helium atom, which comprises two protons  and two neutrons
        • Beta radiation consists of high energy electrons emitted from the nucleus. These electrons have not come from the electron shells or energy levels around the nucleus. Instead, they form when a neutron splits into a proton and an electron. The electron then shoots out of the nucleus at high speed, leaving the new proton behind in the nucleus.
        • Gamma radiation is very short  wavelength, high  frequency electromagne-tic radiation. This is similar to other types of electromagne-tic radiation, such as visible light and X-rays, which can travel long distances.
        • Radiation can be absorbed by substances in its path. For example, alpha radiation travels only a few centimetres in air
          • beta radiation travels tens of centimetres in air
            • gamma radiation travels very large distances.
      • All types of radiation become less intense as they travel further away from the radioactive material this is because the particles or rays become more spread out.
        • Radiation can be absorbed by substances in its path. For example, alpha radiation travels only a few centimetres in air
          • beta radiation travels tens of centimetres in air
            • gamma radiation travels very large distances.
        • The thicker the substance, the more the radiation is absorbed. The three types of radiation penetrate materials in different ways.
    • Half-life
      • The nuclei of radioactive atoms are unstable. They breakdown and change into a completely different type of atom. This is called radioactive decay.
      • It is not possible to predict when an individual atom might decay. But it is possible to measure how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope.
      • "The time it takes for the number of nuclei of the isotope in a sample to halve"
    • Forces on a charged particle
      • Alpha particles are positively charged, beta particles are negatively charged, and gamma radiation is electrically  neutral.
        • opposite charges attract
    • Detecting Radiation
      • Human senses cannot detect alpha, beta or gamma radiation, so we need equipment to do this.
      • Photographic film goes darker when it absorbs radiation, just like it does when it absorbs visible light. The more radiation the film absorbs, the darker it is when it is developed.
        • The Geiger-Muller tube detects radiation. Each time it absorbs radiation, it transmits an electrical pulse to a counting machine
    • Background Radiation
      • Background  radiation is all around us. Some of it comes from natural sources and some comes from artificial sources.
        • rocks and soil - some rocks are radioactive and give off radioactive radon gas
        • cosmic rays - radiation that reaches the Earth from space
        • living things - plants absorb radioactive materials from the soil and these pass up the food chain
        • Human activity has added to background radiation by creating and using artificial sources of radiation. These include medical X-rays,  radioactive fallout from nuclear weapons testing and  radioactive waste from nuclear power stations.

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