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Analyzing the danger of electromagnetic radiation

  1. Apr 3, 2010 #1
    the health hazards posed by electromagnetic radiation should be primarily dependent on three quantities:

    * frequency
    * duration of exposure
    * amount of waves

    the frequency and duration of exposure are easy quantities to determine.

    the question is how is the quantity, or density, of electromagnetic waves calculated?

    can the quantity, or density, of electromagnetic waves for specific appliances and devices be calculated based on the power rating in watts? For example, a 900w microwave, or a 8000w rotating anode xray tube?
  2. jcsd
  3. Apr 3, 2010 #2


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    My best guess is that the electric and magnetic field strengths are the relevant quantities you are after. It would not be possible to calculate these given only the power rating of the device.
  4. Apr 3, 2010 #3
    Also distance plays a important role. (inversely proportional to the square of distance).
  5. Apr 4, 2010 #4


    Staff: Mentor

    Also, the type of tissue exposed is important as is the age of the exposed individual.
  6. Apr 4, 2010 #5


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    Normally the quantity you want is referred to as intensity - that is energy per area per time. Since EM radiation is quantized, this can also be quantified as the number of photons striking a unit area in a unit time. This sums up the suggestions from the previous two posts, since the intensity is proportional to the square of the electric and magnetic fields, and it drops off as the inverse square of the distance from the source.
  7. Apr 4, 2010 #6


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    I agree with physguy, it's probably best to quantify this in terms of power per area (equivalent to energy per area per time).
  8. Apr 4, 2010 #7
    It can be based on it but you'd have to know the efficiency of the device in producing radiation. For example a microwave oven is designed to leak very little radiation and X-ray tubes are quite inefficient.

    Otherwise the approach is correct. Biological dangers from radiation of all types is a vast field that has be studied for many years and a great deal is known about them. Hit the internet and look this stuff up.
  9. Apr 4, 2010 #8
    basically what i'm getting at is,

    what has a higher probability of interacting with a DNA molecule in the body? One x-ray photon, 100,000 x-ray photons, 1 billion x-ray photons, etc... Obviously the Probability of DNA interaction is dependent on the quantity, or concentration.

    So how may this concentration of photons be calculated for a given device, such as a magnetron, xray anode tube, etc...?

    Is the energy per unit area equivalent to this concentration?

    How may the concentration of photons per second emitted by a device be calculated????

    I guess that is the question, if i did not pose it correctly the first time.

    thank you
  10. Apr 4, 2010 #9
    I can't really answer your question but as someone else mentioned, it's a well studied field. It's referred to sometimes as the subject of "ionizing radiation", e.g., see Wikipedia here: http://en.wikipedia.org/wiki/Ionizing_radiation . You can probably start learning about things there.
  11. Apr 4, 2010 #10


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    Yes, ie if you double the wattage of a particular device but leave the frequency the same, you've doubled the number of photons.
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