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Nuclear Radiation and its Uses
In the treatment of cancer, malignant cells are severely damaged by radiation so they cannot
reproduce and will die. Normal tissue is also damaged, but these cells can repair themselves
once treatment is finished. To select the appropriate nuclide for a particular purpose it is…

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4
In alpha decay, a stable helium nucleus 2He is emitted with a charge of +2. The A number
decreases by 4 and the Z number decreases by 2. Alpha decay can be very damaging as it is
very ionising.
A A-4 4
Z X Z-2 Y + 2


Alpha…

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any point (as an exponential curve never reaches zero), a few centimetres of thick lead will
generally stop almost all gamma rays.

Radioactive Decay Rate
A patient undergoing radiation treatment has to receive an appropriate dose. Too little and
the treatment will be ineffective, whereas too much and the radiation…

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This shows that the rate of decrease of the radioactive atoms is proportional to the number
of radioactive atoms present.

Changes in Radioactive Decay Rate

Decay is an exponential decay, meaning it will take the same time to halve each time. The
graph of `N' against `t' shows this. The…

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count rates during an experiment. If not the values will all be too high, leading to an incorrect
half life.

Radiation in Medicine
Isotopes used in medicine have short half lives, and this affects where and how they are
produced. Some are made by nuclear reactors and some by particle…

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1
b + p = e and T1 = T1 + T1
e 1b 1p
2 2 2




Capacitors
Pacemakers are used to control heart beats where there is an irregular heart beat by sending
short pulses of electric current to the heart. To avoid the need for frequent operations,…

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V = Potential Difference (Voltage)(V)

Energy Stored by a Capacitor
When a battery charges the capacitor, energy is transferred from the battery to the
capacitor. When a charge flows between the two points which have an electrical potential
difference between them, the energy transferred is equal to the voltage multiplied…

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Capacitors as Timing Devices
The voltage across a capacitor varies with time in a predictable way when being charged or
discharged through a resistor. This means that it can be used for measuring time intervals.

Capacitor Discharge
A capacitor will discharge quickly at first due to the great repulsion between…

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