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Chapter 42: Q 35 Exercise (page 1237)
How many grays of gamma-ray photons cause the same bio-
logical damage as 30 Gy of alpha radiation?
Hence, 600 Gy of gamma particles rays causes the damage equivalent to the damage caused by 30 Gy of alpha particles.
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Identify the unknown isotope X in the following decays.
The technique known as potassium-argon dating is used to date old lava flows. The potassium isotope 40 K has a 1.28-billionyear half-life and is naturally present at very low levels. 40 K decays by two routes: 89% undergo beta-minus decay into 40 Ca while 11% undergo electron capture to become 40 Ar. Argon is a gas, and there is no argon in flowing lava because the gas escapes. Once the lava solidifies, any argon produced in the decay of 40 K is trapped inside and cannot escape. A geologist brings you a piece of solidified lava in which you find the 40 Ar/ 40 K ratio to be 0.013. What is the age of the rock?
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
A radioactive tracer is made in a nuclear reactor. When it is delivered to a hospital hours later its activity is . The lowest usable level of activity is .
A. What is the tracer鈥檚 half-life?
B. For how long after delivery is the sample usable?
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?
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