i. ii. iii. Forbidden energy gap at 300 K Electron mobility at 300 K Fano factor Si 1.115 eV 1350 cm 2 V- 1 s- 1 .· 0.08 - 0.14 Ge 0.665 eV 3900 cm 2 V- 1 s- 1 0.05 - 0.12 (60 marks)
RADIOISOTOPE UNIT: Sc87102 p. 9 3. (A) Discuss the concepts of specific ionisation and range in relation to ionising radiation. Use these concepts to explain the seemingly paradoxical situation in which alpha particles are less harmful than gamma rays for external hazard, but for internal hazard the opposite is the case. (30 marks) (B) The instantaneous dose rate, R 13 in _Gy s- 1 to tissue containing C, MBq_ kg- 1 of a beta-emitter of average energy E 13 in joule is given by R 13 - 10 6 CE 13 • The internal beta dose accumulated in a given time can be calculated from D where D absorbed dose in Gy ~ - effective half-life in days f - fraction remaining at end of time period Use this information and graph paper to calculate i. the instantaneous dose rate ii. the dose delivered over the first 10 days when 37 MBq of C-14 labelled drug is injected intravenously into an animal containing 540 g of blood. (Assume the biological half-life for the drug is lOO days and the average energy for C-14 is 8 x 10- 15 joule) (30 marks) 4. (A) In a radioactive series A~ B ~ C, prove that the disintegration rate of the parent nuclide A will equal the disintegration rate of the daughter nuclide B when secular equilibrium has become established. (30 marks) (B) i. Describe with examples the system of nomenclature for labelled compounds.
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- Fall '17
- Ionizing radiation