4.2 A radiation with a frequency of 3.13EI 5 Hz releases an electron from a copper plate. The
kinetic energy of the electron is l.70E-18J. Calculate the work function of the plate. Planck's
constant h = 6.63E-34 Js.
(5)
4.3 Use the equation oflinear attenuation to derive an equation of the form y = mx + c.
(5)
4.4 The half-value thickness of a 100 keV X-ray photons passing through aluminium is 2.4E-3
m. If the initial intensity of the beam is 4.2ES W. m- 2 , what would be the intensity of the
beam after passing through a 3 value layers?
(3)
4.5 The increase in the X-ray tube current is proportional to the rate of thermionic emission from
the cathode. List any two effects on the that can be observed with increase in tube current.(2)
QUESTIONS
[20)
5.1 A radionuclide with a physical half life and a biological half-life o/8.0 and 5.6 hours,
respectively, was administered to a patient in Nuclear Medicine Department for imaging.
= = (i) Use the relationship Aeff Ab + Ap to show that Teff
Tp.TTb.
(3)
Tp+ b
(ii) Estimate the effective half-life (in hours) of the radionuclide.
(3)
5.2 Estimate the time elapsed (in seconds) for a radionuclide's activity of 30 mBq reduces with
= 15% of its initial activity and t!. 2.5 days.
(5)
2
5.3 During pair production a positron and electron with mass energies annihilates to produce
photons with energy 0.61 MeV each. Both positron and electron have a mass of9.I09E-31
kg. Estimate the total radiant energy (MeV) transferred into matter. Note: c = 3.00E8 mis
and 1 MeV = 1.602£-13 J.
(5)
5.4 Elucidate both the radical and target theories in terms biological effects of ionizing radiation.
(4)
END
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