The maximum permissible workday dose for occupational exposure to radiation is 11 mrem.A 77 kg laboratory technician absorbs 2.3 mJ of 0.5 MeV gamma rays in a work day.The relative biological efficiency (RBE)for gamma rays is 1.00.The number of gamma-ray photons absorbed by the technician in a workday is closest to:

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The energy of a single gamma-ray photon is:$$E = hf = \frac{hc}{\lambda}$$where h is Planck's constant, f is the frequency, c is the speed of light, and λ is the wavelength.The wavelength of a 0.5 MeV gamma ray is:$$\lambda = \frac{hc}{E} = \frac{(6.626 imes 10^{-34} ext{ J s})(3 imes 10^8 ext{ m/s})}{0.5 imes 10^6 ext{ eV}} = 2.45 imes 10^{-12} ext{ m}$$The number of gamma-ray photons absorbed by the technician is:$$N = \frac{E}{E_\gamma} = \frac{2.3 imes 10^{-3} ext{ J}}{2.45 imes 10^{-12} ext{ J}} = 9.39 imes 10^8$$The closest choice is A) 3 × 10¹⁰.

The Maximum Permissible Workday Dose for Occupational Exposure to Radiation