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B X-rays physics

  1. Apr 9, 2016 #1
    I got question in exam,

    1) How to control hardness of X-ray?

    2) why low frequency of x-ray is used for investigating tissue??

    so in 1) what does controlling hardness means?? and in 2) cant we use high frequency of X-ray ?so that it will penetrate more as tissue are poor absorber of x-ray.
  2. jcsd
  3. Apr 9, 2016 #2
    X-rays are characterized by hard and soft x-rays - hard x-rays are the characteristic wavelengths around 1-2 angstrom and soft ones are spread over about up to 300 angstrom . the hard ones are more penetrating as their frequency is higher and so the more energetic.
    the medical physics/diagnostic pictures need details of the tissue structure and shadow givibg the look of healthy or oherwise disease structures so soft x-ray transmission snaps are taken the hard ones are more used in fatigue or fracture analysis of materials/joints etc.

    to control hardness or softness the tube voltage is raised or lowered - that is the energy of the cathode electrons -if it is higher than threshold value the intensity of hard rays increases -the intensity also depends on the target being used.
    if we have lower accelerating voltage more soft rays of lower frequency can be generated.
    one can visit the site for details;
  4. Apr 9, 2016 #3
    So, why cant we use hard x-ray for scanning tissues as it is less absorber.
  5. Apr 9, 2016 #4
    yes, the more penetrating rays will pass through and one will not get a good radiography picture of the tissue being examined- its less absorber of hard x-rays.its a common statement.
  6. Apr 9, 2016 #5


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    It also helps if you don't kill or seriously irradiate the patient in the process of running diagnostic tests.

    Exposure to x-rays constitutes exposure to radiation, which effects are cumulative in the human body. There are recommended limits to how much radiation an individual is exposed to over a period of time:


    After all, you don't want to go to the doctor to get a broken bone imaged and then wind up with a case of cancer due to exposure to too much radiation. :nb) :frown:
  7. Apr 9, 2016 #6
    Haha ,Now I understand Dude . Thank you :woot:
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