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New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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CHAPTER 1 RADIATION AND RADIOACTIVITY
1 Atomic Model
Atomic Structure Atomic Number Mass Number Isotope
[Mass Number][HKCEE] If the nucleus of an atom is represented by the symbol 214
83 X , it means that this atom has
(1) 131 protons in its nucleus. (2) 83 electrons outside its nucleus. (3) 214 neutrons in its nucleus A. (1) only B. (2) only C. (3) only D. (1) and (2) only E. (2) and (3) only
New Senior Secondary Physics CompulsoryChapter 1 Radiation and Radioactivity
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2 Types of Radiation Radiation
Radioactivity / Nuclear Decay
Compulsory: Radiation and Radioactivity 1 Radiation and Radioactivity
Radioactivity / Nuclear Decay
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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3 , ,α β γ radiations
α radiation β radiation γ radiation Nature
Range
Penetrating Power
Ionizing Power
Blocking
Equation
Detection
In Electric Field In Magnetic Field
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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[Radiations][HKCEE]
In a factory producing aluminium sheets of 1 mm thickness, a thickness gauge is used to monitor the thickness of aluminium sheets. Which of the following states the correct radioactive source to be used in the thickness gauge and the reason behind? Source Reason A. α α particles have strong ionizing power and can be easily detected. B. α The amount of α particles passing through aluminium depends on its thickness. C. β The amount of β particles passing through aluminium depends on its thickness. D. β β particles are less harmful to human beings. E. γ γ radiation has the greatest penetrating power.
[Count Rate][HKCEE] Different absorbers are placed in turn between a radioactive source and a Geiger-Muller tube. Three readingsare taken for each absorber. The following data are obtained:
What type(s) of radiation does the source emit? A. β only B. γ only C. β and γ only D. α , β and γ [Equation][HKCEE] 23892U decays by emitting two α particles and two β particles. Which of the following represents the
resulting nuclide? A. 234
90Th B. 23492U C. 232
88 Ra D. 23090Th E. 222
86 Rn
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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Geiger-Muller Counter
Cloud Chamber
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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4 Decay Process Randomness of Decay Process
Principle of Decay Process
Mathematical Law of Decay Process
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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Half-life and decay constant
[Half-life and discounted rate][HKCEE] In an experiment to measure the half-life of a radioactive isotope in a place where the background count rateis 20 counts per minute, the following results are recorded :
The half-life is about A. 4 minutes B. 6 minutes C. 8 minutes D. 10 minutes E. 12 minutes
[Half-life][HKCEE] The activity of a radioactive source drops from 640 disintegration per second to 40 disintegration per secondin 2 hours. Find the half-life of the source. A. 7.5 minutes B. 15 minutes C. 24 minutes D. 30 minutes E. 60 minutes
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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5 X Ray Nature of X Ray
Origin of X Ray
Uses
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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6 Radiation Application and Safety Application of Radioactivity
Radiation Equivalent Dose
Potential Hazards of Ionizing Radiation
Precautions in Handling Radioactive Sources
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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7 Nuclear Energy Binding Energy
Nuclear Fission Chain Reaction
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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Nuclear Fusion
Mass-Energy Relation
Atomic Mass Unit
New Senior Secondary Physics Compulsory: Radiation and Radioactivity Chapter 1 Radiation and Radioactivity
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[Example] [Nuclear Fusion] Find the energy released in the fusion reaction in the sun: 2 3 4 1
1 1 2 0H H He n+ → + .
Given the following data: Particle Mass (Atomic Mass Unit)
21 H 2.013553 31 H 3.015500 42 He 4.001506
FINAL REMARKS
, ,α β γ radiations are the main theme of the topic of radioactivity. Students are required to understand their
properties, especially on ionization power, range and behavior in electric/magnetic field. Students should also note that radioactivity is a purely random process that does not affected by environmental condition. On the other hand, X ray is also a kind of ionizing radiation but not usually emitted through radioactive nuclei.