Alpha, Beta and Gamma decay
 |
 ,
and
 -rays
differ from each other in many respects including: |
|
|
Alpha
|
Beta
|
Gamma
|
|
| What are these particles made of? |
helium nucleus 2 protons 2neutrons |
electrons which originate in the nucleus | high frequency electromagnetic waves |
| symbol |
|
|
|
| electric charge |
+2
|
-1
|
0
|
| mass |
1 a.m.u.
|
0.0005
a.m.u.
|
0
|
| deflection by electric and magnetic fields |
Yes
|
Yes
|
No
|
| penetrating power |
very weak several cm of air stopped by cardboard |
moderate about 30cm of air stopped by an aluminium foil |
very
penetrating stopped by about 15cm of lead |
| ionising power | very ionising | less ionising than alpha | very low level of ionization |
Nature of
–
rays
Rutherford
succeeded in measuring the specific change of
-rays
and thereby established that they were in fact particles. In 1909
Rutherford and Royd preformed an experiment where they allowed
-particles
to enter a vacuum. They passed a discharge through a chamber and
observed the spectrum of Helium. Together with the result for
q/m they were able to conclude that
-particles
were doubly ionised helium atoms.
Nature of
–
rays
Becquerel measured
the specific change of
-rays
from a number of radioactive sources and found it to be the same as the
value for cathode rays. Therefore
-rays
were in fact electrons.
However,
-particles
come from the nucleus not the outer shells of atoms.
Nature of
–
rays
They were unaffected by electric and magnetic fields and therefore it wasn’t possible to obtain a value for q/m . Perhaps they were unchanged particles or perhaps they were high frequency waves like x-rays. In 1914, Rutherford and Andrade diffracted x-rays using crystals and so confirmed their nature as high frequency electromagnetic radiation.
|
Penetrating ability
|
|
 |
Some examples of
how
,
and
-rays
arise are shown below:
Beta
Gamma
-rays
are different from
or
radiation in that they are electromagnetic waves, not electrically
charged particles. They are the same as light waves or radio waves
except that they have much more energy. rays are just like x-rays except
for where they originate.
-rays,
like
and
,
come from the nucleus of a radioactive atom. X-rays come from outside
the nucleus. Because
-rays
and x-rays have no charge and no mass. They are able to penetrate deeply
through materials.