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Edexcel iGCSE physics…read more

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Atoms and Radioactivity
Atoms: Mass&charge:
Proton: 1 +
Carbon 12 atom. Atomic number 6
Neutron 1 o
(protons), mass number 12 (protons + Electron -
Ionising Radiation:
Alpha ­ helium nuclei ejected from unstable nuclei. Very
ionising but only short range, stopped by thin card.
Beta ­ fast moving elections ejected from unstable nuclei
(neutron breaks down to proton and electron). Less ionising,
longer range, stopped by 1-2mm of aluminium.
Gamma rays ­ electromagnetic photons. Not very ionising but
extremely penetrating and can only be stopped by thick lead.
Massless and without charge.
Nuclear transformations:
Some radioactive isotopes will decay randomly over time,
emitting combinations of radiation.…read more

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Examples of radioactive decay
Each of these reactions will also give off energy as a bi-product.
After an alpha or beta particle has been emitted any surplus
energy is emitted as gamma radiation. These are pure energy and
there is no change to the atomic or mass number or the atom that
emits this.…read more

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Detecting radiation: Background radiation:
Photographic film ­ We are constantly exposed to
becomes fogged when radiation from different natural
exposed to ionising and man made sources.
radiation, used in badges for
workers at risk from
exposure and checked
regularly to ensure safety
limits have not been
Geiger-Muller tube ­
ionising radiation in the tube
ionises the gases within,
allowing a pulse of current
to pass between the
electrodes. This reaches a
counter which clicks when it
detects the radiation.…read more

Slide 5

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Half Life
Radioactive decay: The half-life t1/2 , of a
Random process radioactive isotope is the
However you can predict time taken for half the
how many atoms will decay original number of nuclei to
in a time. decay.
Decay rate measured in Bq, The half life of each
decays per second. particular radioactive
isotope does not change,
As decaying proceeds the
however different isotopes
number of unstable nuclei
have very different half lives.
decreases, as does the rate
of decay.
The proportion of decaying Decay rate, Bq
material stays the same.
t1/2 Time, t…read more

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Applications of radioactivity
Medicine ­ used for x-rays, Hazards of radioactivity:
to kill cancer and other It can kill cells, with a high
illnesses. dose at areas performing
Sterilisation ­ kills of critical functions it can be
microorganisms and fatal.
bacteria on surgical It can also effect genetic
equipment and some food. material of a cell, making it
Radioactive dating ­ by mutate.
measuring the proportion of Workers in the nuclear
carbon-14 (radioactive) in industry wear the badges to
organic material as it decays ensure they aren't exposed
at a predictable rate. You can to strong ionising radiation.
tell roughly how long the Fission reactors produce a
material has been dead. variety of waste that needs
Some inorganic materials to be safely enclosed in lead
can also be dated. or concrete.…read more

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