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The same 1.00 J of ionizing energy from the previous scenario is instead absorbed only by a 2.00 kg forearm. What is the dose to the forearm, in rad?
A2.00 rad
B10.0 rad
C50.0 rad
D100 rad
Answer & Solution
Correct answer: C. 50.0 rad
1. Dose in joules per kilogram is 1.00 J divided by 2.00 kg.
2. Dividing gives 0.500 J/kg.
3. Convert to rad by dividing by 0.01 J/kg per rad: 0.500 divided by 0.01.
4. Dividing gives 50.0 rad.
5. 2.00 rad is the whole-body dose from the earlier scenario, not this concentrated one, and 10.0 or 100 rad do not match this calculation.
6. So 50.0 rad is correct, showing how concentrating the same energy into a smaller mass raises the dose.
_Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.5 Medical Applications of Radioactivity: Diagnostic Imaging and Radiation_
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