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Homework Help: Strange radioactivity question. fast!

  1. Mar 14, 2004 #1
    Strange radioactivity question. plz help fast!

    I know this is in the k-12 forum too but i wasnt sure if this is college level stuff or not so sorrie if this is in the wrong forum.

    And im not telling u to do this for me, i just wanna know some equations and anything that wuld help.

    well, this is a strange question that i have to do a presentation on. I thought it would be easy but i cant find any information after looking through 2 major physics books and searching online. I even asked a tutor about this and still couldnt get any equations i could use. Plz dont bash me if this is the wrong forum. Just direct me to the right one then. This is the problem:
    Radioactive Emission Ranges: For a 35 becquerel (Bq) source of alpha radiation, calculate the rate of particles arriving at a 5.0x10^-4m^2 detector located 20.0 cm, 50.0 cm, 100.0cm, and 130 cm from the source. Repeat the calculations for the same detector at the same positions for a 48 Bq source, a 125 Bq source, and a 1753 Bq source.

    Tabulate and graph your results on a detection rate (Bq) versus distance (cm) graph, with source activity(Bq) as an extra parameter.

    Just need an equation or equations to solve this. You don't have to solve it. Im not tryin to cheat, i just need to know where to even start with this thing. I cant find any equation that includes distance along with detection rate and area. Both books dont have anything. Am i suppose to use several equations together or wat? If anyone has any idea how this is done, plz help me.
  2. jcsd
  3. Mar 15, 2004 #2
    I'm not completely familiar with this term, but if a 5.0x10^-4m^2 detector is what I think it is, the solution would simply be:

    (rate of the source)*(area of the detector)/(surface of the sphere with radius 20 cm,... etc.)
  4. Mar 15, 2004 #3
    In the experiment that we have to do after we do the calculations, we are going to be given a detector device which looks sorta like a large yellow calculator with a square hole on the top. Thats the part that does the detecting. You can switch the top part to have a aluminum foil covering and or some thicker metal covering. The sources we have are these small colored chips that have labels on them tellin u if their beta alpha or gamma. Hope that helps to clarify what the detector is.

    As for the equation u gave out: (rate of the source)*(area of the detector)/(surface of the sphere with radius 20 cm,... etc.), what do u mean by the "surface of the sphere with radius 20 cm,... etc"??????How do u implement the distances and the value of the sources(Bq) into the equations.

    Like from what i see: this is what u plug in right? : (rate of source)(5.0x10^-4m^2)/(????).
  5. Mar 15, 2004 #4
    O and by the way, where or how did u derive that equation from.
  6. Mar 15, 2004 #5
    wait, by surface of the sphere with radius 20 cm, do u mean surface area? Because the detector does not detect 360 degrees. By 20 cm, 50 cm, etc..., i think it means the source chip is placed 20 cm from the tip of the source. So with that in mind, does the equation change...?
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