Essay
Unit 20 Assignment 1
- Institution
- PEARSON (PEARSON)
Unit 20 Medical Physics Techniques Assignment 1 (P M D)
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Laura LatkovaRadioactivity
Particles are emitted from nuclei of unstable
molecules during radioactive decay to make
them more stable. We can measure radioactivity
by Geiger counter. It detects Alpha particles best
as they are strongly ionising but detects also beta
and gamma.
Atom structure
Electron- charge -1, mass 9.110 x 10-28 g
Proton- charge +1, mass 1.6727 x 10-24 g
Neutron -charge 0, mass 1.6750 x 10-24 g
When radioactive decay happens atom looses protons and neutrons during
alpha decay making it more negative, neutrons and protons are lost during
beta decay making it more negative. During gamma decay photons are emitted
so atom looses energy but the structure of atom stays the same.
Alpha particle
Alpha particle is made of two neutrons and two protons and this makes it
positively charged. Because of its heavy mass it is stopped very easily (few
centimetres of air or paper). Its positive charge makes it very ionising. When
electric field is applied alpha particles will be attracted to negative electrode.
Uses- alpha particles are used in smoke detectors. Other particles cannot be
used as they are not affected by smoke. They are also not used as they
produce more radiation what could be harmful.
Beta particle
Beta particles consist of electron which can be stopped by aluminium foil or
meter of air.
Beta – decay is when neutron decays and beta+ decay is when proton decays.
Beta particles are strongly ionising. When electric field is applied, beta particle
will be attracted to positive electrode.
Uses – beta particles a used for control of thickness or foils. Alpha particles are
not used because they would not pass through the foils and gamma particles
would not be affected by the thickness of the foil.
Gamma particles
Gamma particles are emitted usually after alpha and beta particles have been
emitted. It has infinite rage and can be stopped only be lead or one meter of
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