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Chapter 42: Q 33 Exercise (page 1237)
The doctors planning a radiation therapy treatment have determined that a 100 g tumour needs to receive 0.20 J of gamma
radiation. What is the dose in grays?
Hence, the dose in grays is 2 grays.
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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 .
The rate at which a radioactive tracer is lost from a patient’s body is the rate at which the isotope decays plus the rate at which the element is excreted from the body. Medical experiments have shown that stable isotopes of a particular element are excreted with a 6.0 day half-life. A radioactive isotope of the same element has a half-life of 9.0 days. What is the effective half-life of the isotope, in days, in a patient’s body?
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?
An unstable nucleus undergoes alpha decay with the release
of 5.52 MeV of energy. The combined mass of the parent and
daughter nuclei is 452 u. What was the parent nucleus?
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