Question

1) A 1 cm3 cavity of air at STP is exposed to a radiation beam that liberates 3.33 x 10-10 C, under conditions of electronic equilibrium. Compute the dose to air in the chamber. Express your answer in proper metric units. Hint: Assume the energy to liberate this charge is completely absorbed within the cavity, (20 pts)

Answer 1

as given: A 1 cm3 cavity of air at STP is exposed to a radiation beam that liberates 3.33 x 10-10 C, under conditions of electronic equilibrium

at STP air has a density of 0.001293 g cm^-3

1 kg of air has a volume of 7.734x10^5 cm3

1R = 3.33X10^-10 C cm^-3 of air

need to know W for air (energy to produce ion pair in air) = 33.7 eV/ip = 33.7 J/C

SO, the dose to air in the chamber = 2.58X10^-4 C/kg x 33.7 J/C = 8.8X10^-3 J /kg

this equals to = 8.8x10^-3 Gy = 0.88 rad