Nature of radioactive radiations
· A number of experiments were
conducted by Rutherford and
others to determine the exact nature of radiations emitted during radioactive disintegration.
·
Rutherford
and his co-workers discovered that radiations emitted by radioactive substances
were of three different types;
ü α-rays
ü β-rays
ü and (iii) γ-rays.
·
A
radioactive atom does
not emit all the three types of radiations.
Ø The
following experiments provide a clear analysis regarding the nature of
radiations emitted by a radioactive substance.
ü A small quantity of a radioactive
source (radium) was placed in a hole drilled in a lead block so that radiations
are allowed to proceed as a narrow beam in a particular direction towards a
photographic plate.
ü The lead block and the photographic
plate are kept in an evacuated chamber.
ü When an electric field is applied in
the plane of the paper as shown in the diagram these radiations are split into
three distinct groups.
ü One
group is slightly deflected towards the left.
ü They are called α-rays.
ü Another
group is deflected towards the right.
ü They are called β-rays.
ü And
the third is unaffected by the electric field.
ü They are called γ-rays.
Ø The same effect of splitting up of
the radiations can be observed if a strong magnetic field is applied perpendicular to the plane of the
paper and into it.
Ø The
direction of deflection shows that α rays consist of positively charged
particles while β rays consist of negatively charged particles.
Ø γ
rays are neither positive nor negative.
Further
investigations showed that α
particle consists of 2
protons and 2 neutrons, β rays are electrons
and γ rays are electromagnetic radiations of
very high penetrating power.
Link to previous—Natural radioactive definition and discovery
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