Assignment03wAns

Assignment03wAns - Duke University Medical Physics Program...

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Duke University Medical Physics Program MP200 - Radiation Physics Fall 2010 Assignment 03 Due 10/04/10 ( Show your work for each problem. Partial credits are awarded.) 1. The integral R 1 0 xe x dx has the value of (a) 0 (b) 1 2 (c) 1 (d) 3 2 (e) 2 Solution Z 1 0 xe x dx = e x ( x - 1) = e (1 - 1) - e 0 (0 - 1) = 1 2. A 200 keV photon interacts in soft tissue. The energy deposited locally ( in the immediate vicinity of the interaction site) most likely comes from (a) the kinetic energy of a photon-electron (b) the sum of energies of scattered photon and recoil electron fol- lowing Compton scattering. (c) the kinetic energy of a recoil electron following Compton scat- tering.(Scattered photon will most likely deposit energy elsewhere). (d) kinetic energies of electron and positron following pair produc- tion, minus energy of two 511 keV annihilation quanta leaving the site.(pair production not possible below 1 . 022 MeV ). Solution (c) the kinetic energy of a recoil electron following Compton scat- tering.(Scattered photon will most likely deposity energy elsewhere). 3. What radiation absorbed dose of slow neutrons (RBE=2.5) is equiv- alent to a dose of 35 . 0 rad of fast neutrons (RBE = 9.0)? (a) 320 rad (b) 260 rad (c) 160 rad (d) 130 rad (e) 9 . 7 rad Solution: (d) 130 rad 1
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4. A beam of 4 . 5 MeV neutrons is directed at a 30 g tissue sample. Each second, 1 . 5 × 10 6 neutrons strike the sample. If the relative biological effectiveness of these neutrons is 7 . 0, what biologically equivalent dose ( in rem) is received by the sample in 65 seconds ? (a) 0 . 23 rem (b) 0 . 55 rem (c) 1 . 6 rem (d) 19 rem (e)33 rem Solution (c) 1 . 6 rem 5. A physicist wishes to measure the exposure of a beam of gamma rays. The beam is passed through 2 . 00 × 10 - 2 kg of dry air at STP. The beam produces positive ions in the air which have a to- tal charge of 3
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This note was uploaded on 10/30/2010 for the course MP 200 taught by Professor Guna during the Fall '10 term at Duke.

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Assignment03wAns - Duke University Medical Physics Program...

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