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Chapter 42: Q.54 (page 1237)

The fact that A cancels means that all nuclei have this density. It is a staggeringly large density, roughly 1014 times larger than the density of familiar liquids and solids. One early objection to Rutherford’s model of a nuclear atom was that matter simply couldn’t have a density this high. Although we have no direct experience with such matter, nuclear matter really is this dense .

Short Answer

Expert verified

The Ratio of calcium atoms to barium atoms after 2.5 weeks is 0.37.

Step by step solution

01

N=N0e-λκ Nuclei Density :

01

Ca-47atoms:

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Most popular questions from this chapter

a. Draw energy-level diagrams, similar to Figure 42.11, for all A=14nuclei listed in Appendix C. Show all the occupied neutron and proton levels.

b. Which of these nuclei is stable? What is the decay mode of any that are radioactive?

Stars are powered by nuclear reactions that fuse hydrogen into helium. The fate of many stars, once most of the hydrogen is used up, is to collapse, under gravitational pull, into a neutron star. The force of gravity becomes so large that protons and electrons are fused into neutrons in the reaction p++e−→n+ν. The entire star is then a tightly packed ball of neutrons with the density of nuclear matter.

a. Suppose the sun collapses into a neutron star. What will its radius be? Give your answer in km.

b. The sun's rotation period is now 27 days. What will its rotation period be after it collapses?

Rapidly rotating neutron stars emit pulses of radio waves at the rotation frequency and are known as pulsars.

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?

The uranium isotope U238is naturally present at low levels in many soils. One of the nuclei in the decay series of U238is the radon isotope R222n, which decays by emitting a localid="1650487447445" 5.50MeValpha particle with localid="1650487458663" t1/2=3.82days. Radon is a gas, and it tends to seep from soil into basements. The Environmental Protection Agency recommends that homeowners take steps to remove radon, by pumping in fresh air, if the radon activity exceeds 4pCiperliterof air.

a. How many R222natoms are there in 1m3of air if the activity is 4pCiL?

b. The range of alpha particles in air is ≈3cm. Suppose we model a person as a 180-cm-tall, 25-cm-diameter cylinder with a mass of 65kg. Only decays within 3cmof the cylinder can cause exposure, and only ≈50%, of the decays direct the alpha particle toward the person. Determine the dose in mSvperyearfor a person who spends the entire year in a room where the activity is 4pCi/L.

c. Does the EPA recommendation seem appropriate? Why?

Could a 56Fenucleus fission into two 28Alnuclei? Your answer, which should include some calculations, should be based on the curve of binding energy.
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