When the radiation coming out from certain radioactive substance is passed through an electric field, marks of three distinct spot are found on the photographic plate placed in its path. These three marks represent the three kind of rays which are emitted by the radioactive substances. One type of radiation deviated slightly towards the negatively charged plate and were called alpha rays. The second type of radiation deviated substantially towards the positively charged plate and was called the beta rays. The third type of radiation did not deviate at all and was called the gamma rays.
