|
DISCOVERY OF ALPHA, BETA AND
GAMMA RAYS:
Experiments conducted by the British physicist Ernest Rutherford in 1899
showed that radioactive substances emit more
than one kind of ray. He found that part of the radiation is
100 times more penetrating than the rest and can pass through aluminum
foil 1/50 of a millimeter thick. Rutherford named the less penetrating
emanations alpha rays and the more
powerful ones beta rays, after the
first two letters of the Greek alphabet.
Researchers working on these rays found in 1899 that
beta rays were deflected by a magnetic field. It was concluded that the
beta rays are negatively charged particles similar to cathode rays.
In 1903 Rutherford found that alpha rays were deflected
slightly in the opposite direction from beta rays, showing that they are
massive, positively charged particles. Rutherford went on to prove that
alpha rays are nuclei of helium atoms by collecting the rays in a vacuum
tube and showing the buildup of helium gas over several days.
The French chemist Paul Villard discovered the third
kind of radiation in 1900. It was called the
gamma ray. It is unaffected by magnets and is much more penetrating
than alpha particles. Gamma rays were later proven to be a form of electromagnetic
radiation, much like light or X rays, but with much shorter wavelengths.
These shorter wavelengths give gamma rays higher frequencies and make
them even more penetrating than X rays.
|
