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Chapter 42: Q. 53 (page 1237)
A sample contains radioactive atoms of two types, A and B. Initially there are five times as many A atoms as there are B atoms. Two hours later, the numbers of the two atoms are equal. The half-life of A is . What is the half-life of B?
Half life of B is,
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The plutonium isotope 239 Pu has a half-life of 24,000 years and decays by the emission of a 5.2 MeV alpha particle. Plutonium is not especially dangerous if handled because the activity is low and the alpha radiation doesn鈥檛 penetrate the skin. However, there are serious health concerns if even the tiniest particles of plutonium are inhaled and lodge deep in the lungs. This could happen following any kind of fire or explosion that disperses plutonium as dust. Let鈥檚 determine the level of danger. a. Soot particles are roughly 1 mm in diameter, and it is known that these particles can go deep into the lungs. How many atoms are in a 1.0@mm@diameter particle of 239 Pu? The density of plutonium is 19,800 kg/m3 . b. What is the activity, in Bq, of a 1.0@mm@diameter particle? c. The activity of the particle is very small, but the penetrating power of alpha particles is also very small. The alpha particles are all stopped, and each deposits its energy in a 50@mm@diameter sphere around the particle. What is the dose, in mSv/year, to this small sphere of tissue in the lungs? Assume that the tissue density is that of water. d. Is this exposure likely to be significant? How does it compare to the natural background of radiation exposure?
How many grays of gamma-ray photons cause the same bio-
logical damage as 30 Gy of alpha radiation?
What is the age in years of a bone in which the ratio is measured to be?
Could a nucleus fission into two nuclei? Your answer, which should include some calculations, should be based on the curve of binding energy.
a. Is the binding energy of a nucleus with more than, less than, or equal to the binding energy of a nucleus with ? Explain.
b. Is a nucleus with more tightly bound, less tightly bound, or bound equally tightly as a nucleus with ? Explain.
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