NATURE OF RADIOACTIVE RADIATIONS
In 1902,the Newzealand physicist Ernest Rutherford investigated the nature of the radiation emitted by radioactive substance, Pitch blende (U3O8). Ernest Rutherford classified these rays in three types by passing through a strong electric or magnetic field as shown in the figure:
In the experiment , Pitch blende is taken in a lead box with small hoe at the top. when the radiation were passed through two oppositely charged plates( electric fields at right angle to the propagation),then the photographic plate is affected at three positions:
1.The radiations bending towards the negative plate (cathode) are positively charged rays, called alpha rays (α-rays). These are deflected to lesser extent from the original direction showing that they have large mass .
2.The radiations bending toward the positive plate (anode) are the negatively charged rays, called beta rays(β-rays). these rays are deflected to a greater extent showing that they are lighter than α-rays.
3.The radiations which remained undeflected and passes straight forward are neutral in nature and are called gamma rays (γ- rays).
Properties ofα- rays
Properties of β- rays
Properties of γ- rays
COMPARISION AMONG THE PROPERTIES OF α, β & γ
|4.||Mass||Approx. 4 unit|
About 1/1840 of H-atom
About 1/100 of that of α-particle
About 1/20 to 1/10 of that of light
About 30% to 90% of the light
|Same as the speed of light|
|7.||Penetrating power||least(2-7 cm in air)||less (several meters in air)||very high|
Figure: Penetrating power of α, β & γ radiations