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igcse physics notesprinted 117 · PDF 117
124 pagesrevision 46936
printed 117 · PDF 117
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charged protons so when it collides with the air molecule, the electron it will
knock out will likely be charged as well.
A beta particle moves much faster than an alpha particle and has lesser
kinetic energy, so is likely to travel straight through an air molecule rather
than interacting with it. It also has a lesser charge than an alpha particle.
Gamma radiation is uncharged and moves at the speed of light. It also has
no mass. It is absorbed least in thin air due to this and is thus the least
ionizing.
Radioactive decay
Radioactive decay is spontaneous and random and can emit three types of
radiation, as discussed above. Out of these three types of radiation, alpha
decay and beta decay cause the nucleus to change to that of a different
element.
For alpha decay, a helium atom(2 protons and 2 neutrons) are given out.
For beta decay, a neutron changes to an electron and a proton and the
electron is given out.
For gamma decay, pure energy is given out.
This can be exemplified below:
Note: The atomic numbers and nucleon numbers on both hand sides of the
equation must be equal.
After decaying, the nuclei become more stable and there is a reduction in
the number of excess neutrons or heaviness of the atom.