ch32 - CHAPTER 32 IONIZING RADIATION, NUCLEAR ENERGY, AND...

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Unformatted text preview: CHAPTER 32 IONIZING RADIATION, NUCLEAR ENERGY, AND ELEMENTARY PARTICLES CONCEPTUAL QUESTIONS ____________________________________________________________________________________________ 1. REASONING AND SOLUTION The RBE, or relative biological effectiveness, of a particular type of radiation compares the dose of that radiation needed to produce a certain biological effect to the dose of 200 keV X-rays needed to produce the same biological effect. The RBE depends on the nature of the ionizing radiation and the type of tissue that is being irradiated. Therefore, if two different types of radiation have the same RBE, this does not mean that each type delivers the same amount of energy to the tissue that it irradiates. Rather, it implies that the two different types of radiation are equally effective in producing the same biological effect on the same kind of tissue. ____________________________________________________________________________________________ 2. REASONING AND SOLUTION When a dentist X-rays your teeth, a lead apron is placed over your chest and lower body. The purpose of this apron is to protect the tissues on your chest and lower body from the ionizing effect of the X-rays. The thickness of the lead is chosen so that the apron blocks the penetration of the X-rays. ____________________________________________________________________________________________ 3. REASONING AND SOLUTION a. The units "rads" and "grays" are used to express the absorbed dose of ionizing radiation. According to Equation 32.2, the absorbed dose is equal to the energy absorbed from the radiation per unit mass of the absorbing material. The gray (Gy) is the SI unit for absorbed dose and is equal to 1 J/kg. The relationship between rads and grays is: 1 rad = 0.01 gray. b. The units "rads" and "roentgens" are not related. The rad is used to express the absorbed dose , and 1 rad = 0.01 J/kg. The roentgen is used to express the exposure , and 1 roentgen = 2.58 10 4 C/kg. The exposure expresses the ionizing abilities of X-rays or rays in air, while the absorbed dose specifies the amount of energy absorbed per kilogram of absorbing material. ____________________________________________________________________________________________ 4. SSM REASONING AND SOLUTION In any nuclear reaction, the following quantities are conserved: (1) mass / energy; (2) electric charge, (3) linear momentum, (4) angular momentum, and (5) nucleon number. a. 60 corresponds to the reaction 62 28 29 Ni ( , ) Cu p 2 4 He + 28 60 Ni 29 62 Cu + 1 1 H Chapter 32 Conceptual Questions 1587 The nucleon number for the reactants is 4 + 60 = 64, while the nucleon number of the products is 62 + 1 = 63. Therefore, this reaction does not occur, because it violates the conservation of nucleon number....
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This note was uploaded on 05/09/2008 for the course PHYS 25 taught by Professor Holland during the Spring '08 term at Pacific.

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ch32 - CHAPTER 32 IONIZING RADIATION, NUCLEAR ENERGY, AND...

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