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Effects Of EM on Matter

  1. Jun 5, 2005 #1

    jq

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    I am trying to start a discussion on the Effects of EM on matter (biological, electronic and other matter).

    I am trying to understand the relationship between quantities Electromagnetic (EM) and effects on matter. In particular many types of EM used for medical purposes and can reach certain parts of the body with out effect others (Cutting,heating,imaging,resonating,flexing...) in (MRI,CAT,Laser Surgery...). I am trying to understand how this is possible and the quantiles involved. The formula E=hf is used to define absorption in my sources, but they talk about energy needed to bring to the atom to the next energy level?

    -So usably given a mix (wave length, frequency) and (Watts or joules). From this I am attempting to find what matter will absorption the frequency? Especially when going through matter of different densities.
    -And what quantities (Volts, Charge,Pressure,Force,Energy,Temperature) that matter will be induced with?
    -Any known biological effects caused by Absorptions?
     
  2. jcsd
  3. Jun 7, 2005 #2
    It is not a simple subject. For example, we all know that humans are not transparent in optical region, which means that light should be absorbed and reflected, mostly on skin. However you can see that laser lat can partially go through your hand.

    X-rays can go deeper into body, and they can eventually go through the body. However, humans are not completely transparent in X-ray region as well, so we can look on something inside themusing this electromagnetic region.

    Absorption really depends on the mechanism of the wave- charge interaction, which depends on what material you consider. basically electromagnetic wave interacts only with electrons. Ions are much heavier, they gain little speed under the wave, so it is more difficult for them to absorb energy.

    There is also another effect, scattering. It is connected with absorption and reflection, but it make sense to consider it separately in case of non-uniform matter. For example, it is light scattering which is responsible for the image blurring when we see through the hot air.
     
  4. Jun 7, 2005 #3

    SGT

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    Another effect of EM on matter is ionization: the separation of electrons from their atoms. If the wavelength is appropriate, the absorbed EM can provide enough energy to an electron to allow it to abandon the atom.
    Ionization then triggers chemical reactions. If those reactions occur in an atom in a molecule of DNA, the DNA will be altered and so will be cellular multiplication. This could even produce cancer.
    Only very short wavelenghts (UV, gamma rays) will cause ionization. That is why those types of radiation can cause cancer.
     
  5. Jun 7, 2005 #4

    Claude Bile

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    The effect of long-term exposure to long-wave radiation (such as that produced by mobile phones), particularly to the brain, has not been conclusively determined. If there is an effect, the mechanism is probably much more subtle than those mentioned already.

    Claude.
     
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