RADIOACTIVITY
Radioactivity is a nuclear phenomenon, was first discovered by Henri becquerel in
1896. Becquerel left some uranium salts wrapped in a black paper on a
photographic plate, and was lying in a dark room. when he developed the
photographic plate, he found that the plate was affected. He repeated the
experiment and concluded that uranium and its salts emit invisible radiations,
which can pass through paper wood etc, and also affect the photographic plate. the
radiations were found to have alpha and beta particles and gamma radiations.
Hence radioactivity is the processes by which a nuclei undergo disintegration and
emits either alpha, beta or gamma radiations. during radioactive process atom
changes its atomic number and chemical identity.
The term activity refers to disintegration rate of radioisotope and measured by unit
curie[Ci].one curie is the number of disintegration per second from 1g of radium,
and is found to be 3.7x1010 dps.
238U92 -> 234Th90 + 2He4
Radioisotope: Atom with unstable nuclei that performs radioactivity is called
radioisotope.
The initial atom that undergoes disintegration is called parent and the end product
is called daughter. Radioactivity may be classified as,
1. Natural radioactivity
2. Artificial radioactivity
Natural radioactivity
The phenomenon of spontaneous emission of rays such as alpha, beta, gamma by
heavy elements having atomic number greater then 82 is called natural
radioactivity.
Natural radioactivity originates from various sources,
Radioactive elements contained in the soil
Cosmic radiation that comes from the space and sun, when considering
altitude cosmic radiation 1.5 times higher at 1500m above sea level.
