The binding energy of Sodium is 2.28 eV. Calculate the number of
photoelectrons ejected from a 1.00 mm2 area of Sodium metal by 500-nm
electromagnetic radiation having an intensity of 1.30 kW/m2. What power is
carried away by the electrons? [10 marks]
B. A 60-kg person accidentally ingests a small source of alpha particles
(RBE=15). The activity of the source is 0.04 Ci, the half-life of the source is 110
years, and each alpha particle emitted has an energy of 0.586 MeV. It takes 12
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hours for the alpha source to pass through the person’s digestive system and
exit the body.
i. How many alpha particles are absorbed by the person (assume that 100
percent of the alpha particles emitted by the source are absorbed by the
person)? [6 marks]
ii. How much energy, in Joules, is deposited in the person by the source?
[2 marks]
iii. What is the absorbed dose in rad? [1 mark]
iv. What is the absorbed dose in rem? [1 mark]
C. A 70-kg person experiences a whole-body exposure to alpha radiation
(RBE=15) with energy 4.77 MeV. A total of 6.25×1012 alpha particles are
absorbed.
i. What is the absorbed dose in rad? [7 marks]
ii. What is the equivalent dose in rem? [3 marks]
iii. If the source is 0.0320 gram of Radium-226 (half-life 1,600 years)
somewhere in the body, what is the activity of this source? [5 marks]
iv. If all the alpha particles produced are absorbed, what time is required
for this dose to be delivered? [5 marks]
D. Suppose that 0.1 kg of ice at an initial temperature of -10°C are put into 0.40
kg of water at an initial temperature of 20°C. Assume the final temperature is
0°C. How many grams of ice will melt? Specific heat capacity of water is 4,200
J/kg/°C. Specific heat of fusion of water is 336,000 J/kg and specific heat
capacity of ice is 2,100 J/kg/°C.