A chest x ray uses 10 keV photons with an RBE of 0.85. A 60 kg person receives a 0.30 mSv dose from one chest x ray that exposes 25% of the patient’s body. How many x ray photons are absorbed in the patient’s body?
Then the dose is Given by
The amount of energy received by the body is
photons absorbed patient's body=Therefore, the number of X-ray photons absorbed by the body is the ratio of the energy absorbed by the body and the energy absorbed by the photons
You learned in Chapter 41 that the binding energy of the electron in a hydrogen atom is .
a. By how much does the mass decrease when a hydrogen atom is formed from a proton and an electron? Give your answer both in atomic mass units and as a percentage of the mass of the hydrogen atom.
b. By how much does the mass decrease when a helium nucleus is formed from two protons and two neutrons? Give your answer both in atomic mass units and as a percentage of the mass of the helium nucleus.
c. Compare your answers to parts a and b. Why do you hear it said that mass is “lost” in nuclear reactions but not in chemical reactions?
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