edexcel P2 topic 6

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Topic 6 ­ using radioactive materials
Background radiation
Most background radiation comes from natural sources while
artificial background radiation comes from medical examinations.
The radioactivity of a source is measured using half-life.
Background radiation is the low level radiation that's around us all
the time. Natural sources are:
source Type of radiation
Cosmic Radiation from the sun that
rays reaches the earth from space
animals Animals emit natural levels of
radiation
Rocks Some rocks give off radioactive
radon gas. Radon gas tends to get
trapped inside people's houses
and this increases background
radiation. However the radon
concentration varies depending
on what type of rock and also the
region.
Soil and Radioactive materials from rocks
plants in the ground are absorbed by
the soil and passed on to the
plants
Background radiation comes from naturally occurring unstable
isotopes in air, in food, in building materials and in rocks.
There is a small amount of radiation due to human activity for
example nuclear explosions or dumped nuclear waste.

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Uses of radiation
Ionisation is when radioactive
materials ionise other materials and
turn the atoms into charged particles - ions. This can be a useful
thing:
Uses of alpha radiation
Alpha radiation is used in smoke detectors. Radioactive americium
releases alpha radiation which ionises the air inside the detector
and causes a current to flow. The smoke from the fire absorbs the
alpha radiation and this alters the ionisation and stops the current,
triggering the alarm.…read more

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The
radioactive source must have a long half-life so that it doesn't decay
too quickly. It needs to beta because the paper will partly block the
radiation and if it all goes through or none, the reading will not
change at all as the thickness changes.…read more

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A short half-life means the activity falls quickly because lots of the
nuclei decay quickly and a long half-life means the activity falls more
slowly because most of the nuclei don't decay for a long time.
The activity of a radioactive isotope is measured in Becquerel (Bq). 1
Bq is 1 decay per second. This can be measured with a
Geiger-Muller tube.…read more

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Dangers of radioactivity
Ionising radiation can cause tissue damage and cell mutation. Alpha,
beta and gamma radiation enter the living cell and collide with
molecules which causes the molecules to break into smaller
fragment. As a result ionisation happens which leads to tissue
damage. Radiation affects DNA, causing mutations. These divide
uncontrollably which leads to cancer. Higher doses kill the cell
completely.…read more

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Exposure times are limited
Keep source at arm's length to keep it as far from the body
as possible
Risks
Development of radioactive materials in 20th century led to
many workers death. The materials were new so people did
not realise they could be dangerous. The risks can be assessed
by measuring chance of occurring in a large sample.
Safe dose that people receive was based on rate of cancer in
workers exposed to radiation over years.…read more

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Disadvantages:
Public perceptions are negative ­ nuclear power dangerous
Worried that nuclear waste can never be disposed safely.
There is a danger of leaks and pollution of land, rivers and
oceans. Contamination of huge areas. People say the energy
generated is not worth the risk of nuclear waste accidents.
And its non - renewable
Nuclear power carry risks of leaks from the power station or a
major catastrophe like Chernobyl
Nuclear fission creates lots of radioactive waste products.…read more

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