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Homework Help: Collisions between the alpha particles and air molecules

  1. Mar 10, 2005 #1
    i will be appearing for my a levs in a couple of months and this is a 'design experiment' question i need help with. i haven't ever designed an experiment and help will be appreciated.


    'Alpha particles from a particular radioactive source have a range of about 6 or 7 cm. This is because the kinetic energy of the alpha particles is continually being transferred to air molecules due to collisions between the alpha particles and air molecules.
    Design a laboratory experiment to investigate how the range of alpha particles in air is affected by the air pressure. In your account it is expected that you will:

    a) Draw a diagram showing how the aparatus would be used in your investigation (.. i suppose this won't be possible here...)

    b) Explain clearly the procedure to be followed

    c) name the alpha particle detector which you would use.

    d) state any safety precautions which may need to be taken when performing this experiment.
  2. jcsd
  3. Mar 11, 2005 #2
    draw a picture of a geiger counter in a pressurized container.

    explain that you will use a computer to capture the gieger hits over a broad range of time with background corrections for each time range. you will vary the distance by fixed distance levels and use a fixed source of radiation, probably those little disks. then you just vary the pressure level, and retest at each distance, graph, fit, compare.

    any standard geiger counter should work, find one that is sensitive to alpha, this is some physics stuff i dont really know. wasnt really aware that there were different gieger counters, but i did this experiment at fixed pressure last semester, and the given geiger counter for gamma, alpha, and beta worked fine for all three, but the range on the alpha was really short compared to the other two.

    keep your distance from the counter, use a weak source, and make sure the pressure container is capable of containing the pressure your are working with.

    other than that, you just need to think the details through. be really thorough and complete, you can never be too anal with lab experiment design. you want to eliminate as much error as realistically possible. alpha isnt that dangerous, as long as you are using a weak source.

    there are more specific detectors, silicon diode based detectors that are super sensitive that would be better, among other things.

    id use the gm-90 usb counter and some real cheap software. as for alpha source, thats up to you.
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