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An X-ray operates at 30000V and the current through it is 2mA. Given that the charge of an electron is 1.6 x 10-19C, h = 6.63 x 10-34JS, speed of light, C = 3.0 x 108m/s, calculate:-

  1. the maximum kinetic energy of the electrons when hitting the target. 
  2. the number of electrons hitting the target per second.
  3. the minimum wavelength of the X-rays emitted.

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  1.  Ke = ½MV2 = eV
    = 1.6 × 10-19 × (30,000)2
    = 1.44 × 10-10J
     

  2. I=ne
    2 x 10-3 = n x 1.6 x 10-19
    n= 2x 10-3
        1.6 x 10-19
    =1.25 x 1016 electrons
     

  3. hfmax = eV But fmaxe/λmin
    e/λmin = eV
    λmin =hc/eV 
    = 6.63 x 10-34 x 3 x 108
          1.44 x 10-10
    = 1.38 x 10-15m


 

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