Download Alpha, beta and gamma radiation

Starter – fundamental forces
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RADIATION
• Alpha
• Beta
• Gamma
Alpha, beta and gamma radiation
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Properties of a, b and g radiation
If a source emits an unknown type of radiation, which property
of alpha, beta and gamma radiation could most easily be used
to find out what the source emits?
paper
aluminium
lead
Absorption provides a simple test. Remember that a source
may emit more than one type of radiation.
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Hazards and applications
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Which type of radiation?
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The Effect of a Magnetic Field on Radiation
Press a button to see the effect of a magnetic field on different types
of radiation...
The Effect of an Electric Field on Radiation
Press a button to see the effect of an electric field on different types
of radiation...
Energy of emitted beta particles – what’s
going on here?
The neutrino
A serious difficulty is that beta particles emitted are shown to have a continuous
range of energies up to some maximum value Emax. Except for the very small recoil
energy of the proton, all of the available reaction energy should be given to the
electron
However we find that they all have less than this value in a continuous fashion from 0
eV right up to this maximum energy. This is indeed very extraordinary. There are no
alpha particles or gamma rays emitted along with the electron and it is difficult to see
how an electron could be emitted from the nucleus with an energy less than the
maximum possible one. It appeared that beta decay violates the principle of
conservation of energy!
The answer was found by the Austrian physicist Wolfgang Pauli. Pauli suggested that
a third particle, with zero rest mass (or nearly zero rest mass), was emitted during
beta decay. The variability of the energy of the beta rays is accounted for by this
extra particle ejected by the nucleus which can have a range of energies
corresponding to the beta particle energy spectrum. Sometimes the electron gets
nearly all the energy and sometimes the mystery particle does.
However, for all cases, the sum of the electron's energy and the mystery particle's
energy gives a constant value. As the conservation of electric charge is not violated
during beta decay, this new particle must also have zero charge
Pauli called this particle a neutrino (meaning `little neutral one') and it is this
particle that carries off the `missing energy' from the beta emission spectrum.