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Homework Help: Radioactvity - Specimen CCEA papers

  1. Feb 22, 2012 #1
    1. The problem statement, all variables and given/known data

    - 3c(i) A radioactive source is known to emit two types of radation. To find out which types, the apparatus shown below was set up. Three different materials were, in turn, places between the source and the detector.

    Here it shows source, absorber, detector and counter. Then we have a table below.

    No material present: 600
    Thin sheet of paper: 310
    Aluminium 1cm thick - 308
    Lead 1cm thick - 145

    Which two radations did the source emit? Give reasons for your answer.

    And also we have one more - quite similar one, actually.

    3(d) - It explains some oil industries use same oil flow and need to know when one company's oil stops and another company's begins. Each company adds a radioactive substance to the first part of the batch - a detector and counter will then show when the oil containing this radioisotope passes.

    Which type of radation must be emitted by the radioisotope in the oil for this method to work? Explain your answer?

    2. Relevant equations
    None, actually.

    3. The attempt at a solution
    The first one

    3c(i) - Beta. Beta radation is stopped by alluminium and therefore it is equal to thin sheet of paper but less than lead since it stops it.

    Gamma - Can penetrate thin sheet of paper and alluminium but it is greatly reduced by lead.

    The second one

    Gamma - Travels several metres and therefore it can go through the tube but be absorbed by thick metal pipe mostly.
  2. jcsd
  3. Feb 22, 2012 #2


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    Homework Helper

    In case 1, the paper has reduced the radiation as much as the Al, so I think there must have been a component of the original which is stopped by a piece of paper - and that is not β nor γ. The Al does not make a significant difference, so the radiation that can get through paper, but can't get through Al must not be present.

    For part 2, I like your choice of radiation, but I would simply say because neither α nor β would be able to get through the heavy metal pipes used to transport Oil.
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