You have learnt in the earlier chapters that flow of electrons constitutes an electric current and current can be generated from a battery or a generator. Scientists later discovered that there are many other ways of producing the stream of electrons. This knowledge has led to further developments in many fields of science and technology. In fact it can be said that the study of atomic physics started with the conduction of electricity through gases in discharge tube. One of the ways of producing a beam of electrons is 'Thermionic emission'.
Radioactivity, radioactive rays and their use in medicine for diagnosis and treatment of some of the diseases is a common knowledge in these days of advanced knowledge of science and medicine.
Radioactivity was discovered by Henry Becquerel in 1896 accidentally while working with some uranium salts. It was Madam Curie and Pierie Curie that renamed the phenomenon as 'radioactivity' later when they discovered polonium and radium from pitch blende an ore of uranium, which have much higher rate of activity.
Let us now study these phenomenon in detail.
