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Avoid unnecessary exposure.

Avoid direct contact with the source.

Never point the source to any people.

Radioactive sources must be stored in places out of reach of the public.

Sources must be stored inside lead box against leakage of radioactive radiation.

Long forceps must be used in handling the sources.

Thick lead shields should be installed.

Radiation symbols must be displayed at all radiation laboratories.

Radiation workers have to wear special protective clothing and gloves.

Use film badges to measure the amount of radiation the radiation workers receive during a certain period.

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Due to high penetrating power ( beta and gamma ) nd high ionizing power of alpha particles, radioactive sources are dangerous to human life.

They cause damage to or destruction of living cells.

they cause genetic changes in living cells.

they cause cancer.

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The half life of a sample of radioactive element is defined as the time taken for half of the unstable nuclei to decay.

for example, the half life of radium is 1600 years. starting with 20g of radium, 10g will have decayed after 1600 years, leaving 10g. 15g will have decayed after 3200 years,laving 5 g and so on.

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When beta particles are emitted the mass number remains same, but the proton number increase by 1. Here neutron decays into a proton and a beta particle. So the change in atomic number cause to form a new atom.

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When an atom emits alpha , beta particles the change happens in thenucleus. When alpha particles are emitted the atom loses 2 proton and 2 neutron so the nucleon number of the atom decrease by 4 and atomic number by 2,as a result new atom is formed.

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8.  State that during α - or β -decay the nucleus changesto that of a different element

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8.  State that during α - or β -decay the nucleus changesto that of a different element

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When the atomic number of an element reaches 82, the repulsion between proton makes the nucleus unstable and the nucleus tends to break up into smaller parts.

When this happens alpha particles, beta particles or gamma rays may be emitted from the nucleus. This the called Radioactive decay or Disinttegration.

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6.Give and explain examples of practicalapplications of α , β  and γ -emissions

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6.Give and explain examples of practicalapplications of α , β  and γ -emissions

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Smoke detector- alpha radiation

Thickness measurement- beta radiation

Medical diagnosis – gamma radiation

Fault detection – gamma radiation

Radiation therapy – gamma radiation

Food irradiation – gamma radiation

Sterilisation -  gamma radiation

Radioactive tracing – gamma radiation

Radioactive labeling- gamma radiation

Radiocarbondating.

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5.  Deflection in electric fieldsand in magnetic fields

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5.  Deflection in electric fieldsand in magnetic fields

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a) Gamma rays are not deflected in any field.

b) Alpha particles are attracted towards negatively charged plate and beta are attracted towards positively charged plate.
c) When alpha and beta move they constitute electric current and they are deflected in magnetic field. Deflection is found using Fleming’s left hand rule.

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4.  Characteristics of the three types of radiation.

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4.  Characteristics of the three types of radiation.

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 3.  The random nature of radioactive emission

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 3.  The random nature of radioactive emission

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Radioactive decay occur randomly over space and time. In other words, it is impossible to state exactly which nucleus and exactly when a particular nucleus will decay.

Radioactive decay is not affected by chemical reaction or any change in physical conditions such as temperature, pressure, electric field or magnetic field and so on.

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2.  







 The detection of α -particles, β -particles and
γ -rays

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2.  







 The detection of α -particles, β -particles and
γ -rays

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Photo graphic film

a) Photographic films will be blackened by all the three types of radiations when they fall on the film.

b) Photo graphic film is mainly used by radiation workers. Its mainly used radiation workers. It measures the quantity of radiation fallen on the worker within a certain period.

Geiger Muller Tuber ( GM Tube)

a) Argon gas is ionized when radiation enters the GM Tuber.

b) The positive ions are attracted to the cathode and negative ions are attracted to the anode.

c) A pulse of current is produced.

d) The pulse of current is detected by a scale or ratemeter.

e) The reading on the scaler or ratemeter reflects the radiation level.

Diffusion Cloud Chamber

a) When radiation passes through the dense vapour, air is ionized and ions are formed.

b) The alcohol vapour condenses on the ions.

c) The ionizing particles therefore leave tracks in the cloud chamber.

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1.  Understanding of background radiation

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1.  Understanding of background radiation

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Level of radiation all the time is know as background radiation.

sources of background radiations are -

1. Cosmic radiation that is coming from outer space.

2. The radiations coming from environment, rock, concrete or soil.