Compléter FUNPHYS 18: Radiation Safety (p1)Version en ligne -Discuss the interactions of decay products with biological tissue. -Differentiate between the photoelectric effect, the Compton effect, pair production & pair annihilation. -Demonstrate the role of the radioactive decay equation in calculations of half life. -Differentiate between; activity, Becquerel, the Curie absorbed dose and quality factor. par Zainab Nabeel 1 Everybody is to a wide range of radiation from different sources , e . g . , IR , e - m , etc ? . However , certain types of radiation are said to be ionizing , i . e . have sufficiently large energy to electrons within a tissue . Common types of ionizing radiation are a - and b - particles , - , and gamma rays . Often , such radiation can leave a trail of ( ) ionization within the tissue , and this can seriously disrupt sensitive biological systems ( living cells ) within the body . There are 4 major categories of radiation that are of interest in the biological and medical sciences : 1 . Positive ions ( e . g . a - particles ) . 2 . Electrons ( e . g . b - particles ) . 3 . Photons ( x - rays and ) . 4 . Neutrons . All of these are capable of producing biological damage by their ionizing effect on biological tissue . Positive Ions ( a - particles or Protons ) have very ranges in matter ( stopping distance ~ 1 / density ) . A 5 MeV a - particle would travel about 4 cm in air , but cannot penetrate a thin sheet of paper . The relatively large , charged , slow - moving a - particle interacts very well with atoms ( and their electrons ) , providing a high degree of ionization in its path . A 5 MeV a - particle traveling through tissue deposits energy ( through collisions ) at about keV / micrometer . When its kinetic energy decreases to approximately 1 MeV , the a - particle acquires 2 electrons and becomes a helium atom ( which comes to rest after a few collisions ) . Its stopping distance = Energy Change ( 4 MeV ) / 100 keV / micrometer = 0 . 04 mm ( within the tissue ) Since the a - particle is so much more massive than an electron , it is not easily within the tissue ( i . e its path is close to a straight line ) . b - particles resulting from decay have energies ranging from a few keV up to ~ MeV . Since the electron mass is so small , the b - particle velocity will be considerably greater than that of an a - particle ( for particles with the same energy ) . The rate of energy per interaction for a b - particle is ~ 1 / ( velocity ) ^2 . The rate of energy loss for a b - particle within the tissue is much than that for an a - particle . Ex : The rate at which a b - particle energy in tissue is ~ 0 . 25 keV / mm . ( i . e . ~ times less than that for an a - particle ) Hence , the range of a 1 MeV b - particle within tissue can be calculated as : in Tissue = 1 MeV / 0 . 25 keV / micrometer = 4 mm ( i . e . much further than an a - particle would ) . However , there are two consequences of lower energy rates , and small masses for b - particles : a ) The amount of ionization along the path of the b - particle is much lower than for an - . b ) The small electron mass results in a large deflection after each with an atomic electron . b - particles do not travel in straight lines , but ? wander ? randomly .
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