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Chapter 42: Q 20 Exercise (page 1236)
A sample of 1.0x1010atoms that decay by alpha emission
has a half-life of 100 min. How many alpha particles are emitted
between t = 50 min and t = 200 min?
Therefore are emitted between t=50 min and t = 200 min.
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The uranium isotope is naturally present at low levels in many soils. One of the nuclei in the decay series of is the radon isotope , which decays by emitting a localid="1650487447445" alpha particle with localid="1650487458663" days. 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 of air.
a. How many atoms are there in of air if the activity is ?
b. The range of alpha particles in air is . Suppose we model a person as a -tall, -diameter cylinder with a mass of . Only decays within of the cylinder can cause exposure, and only , of the decays direct the alpha particle toward the person. Determine the dose in for a person who spends the entire year in a room where the activity is .
c. Does the EPA recommendation seem appropriate? Why?
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- S n + n. 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鈥檚 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
Identify the unknown isotope X in the following decays.
Does each nuclear energy-level diagram in FIGURE Q42.4 represent a nuclear ground state, an excited nuclear state, or an impossible nucleus? Explain.
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 . 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 .
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.
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