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Name: Unknown
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
Please explain how beta particles can be positive.



Replies:
Technically, beta particles are electrons produced by radioactive decay, when a neutron changes into a proton, an electron which is ejected from the nucleus, and a neutrino (also ejected, but very hard to detect), are negatively charged. However, some radioactive processes result in the emission of a positron, a particle of the same mass as an electron but positively charged. Both processes are referred to as "beta decay". Beta particles were discovered by Madame Curie and Becquerel in the late 1890's. Positrons were not detected until 1933 (and this was in cosmic rays, not radioactive decay); in fact, their existence was predicted on theoretical grounds by Dirac, three years before they were detected! A positron has only a fleeting existence, at least in our part of the universe, since when it meets up with an electron the two annihilate, producing gamma rays. (This process is called pair annihilation.) That is probably why positrons were not detected in radioactive decay until much later; they annihilate long before they can show themselves in the sort of detector used by Curie & Becquerel.

R.C. Winther



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