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Chapter 42: Q 32 Exercise (page 1237)

What is the total energy (in MeV) released in the beta decay

of a neutron?

Short Answer

Expert verified

Therefore, the total energy released is0.78MeV

Step by step solution

01

Given information

Beta decay of a neutron.

02

Explanation

We need to find the energy released during neutron beta decay.

The decay is given as:

np++e-+v¯

We find the value of Δm:

Δm=m(n)-mp+-me-Δm=939.57MeV/c2-938.28MeV/c2-0.51MeV/c2Δm=0.78MeV/c2

03

Calculations

The energy released is calculated as:

E=Δmc2E=0.78MeV/c2c2E=0.78MeV

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Most popular questions from this chapter

Are the following decays possible? If not, why not?

a.Th232(Z=90)U236(Z=92)+αb.Pu238(Z=94)U236(Z=92)+αc.B11(Z=5)B11(Z=5)+γd.P33(Z=15)S32(Z=16)+e-

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’t 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’s 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?

We’ve noted that fewer than 10%of the known nuclei are stable (i.e., not radioactive). Because nuclei are characterized by two independent numbers, Nand Z, it is useful to show the known nuclei on a plot of neutron number Nversus proton numberZ.

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?

How many half-lives must elapse until (a) 90% and (b) 99% of a radioactive sample of atoms has decayed?

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