NUCLEAR RADIOACTIVITY
Isotope:
They are atoms of the same element having the same proton number but different neutron
number.
This is how we write an element name in physics.
14µ represents mass number (number of protons and neutrons)
6e represents the atomic number (number of protons)
Writing ‘e’ next to the atomic number tells that there is this much elementary charge in a nucleus of
this element.
In this case it is 6 x (1.6 x 10-19) C
Writing µ next to 14 indicates the mass of a proton/neutron
In this case it is 14 x (1.67 x 10-27) kg
Note: Both of the values for µ and e will be given in exam
Radioactivity:
The random and spontaneous decay of unstable nuclei releasing β-, β+, γ and 4µ2e α
radiations.
Writing the words ‘random’ and ‘spontaneous’ are very important.
Random:
Each unstable nucleus has an equally likely probability of decaying.
For example, we do not know, out of these 5, which will decay when.
, This phenomenon is experienced by fluctuations in the readings.
If a graph is plotted about number of nuclei decaying, it would look
something like this.
Spontaneous:
The rate of decay is not affected by external factors.
Example: Changing temperature, pressure etc.
This can be experienced by no change due to change in temperature/pressure or
any other external factor.
Half Life:
The time required for the initial rate of decay to become half of its original value.
n = 120s
Initial decay= 1024
Final decay = 16
Time passed = ?
n passed = ?
Initial decay * 1/2half lives = Final decay
1024 * 1/2half lives = 16
= 2half lives
64 = 2half lives
Isotope:
They are atoms of the same element having the same proton number but different neutron
number.
This is how we write an element name in physics.
14µ represents mass number (number of protons and neutrons)
6e represents the atomic number (number of protons)
Writing ‘e’ next to the atomic number tells that there is this much elementary charge in a nucleus of
this element.
In this case it is 6 x (1.6 x 10-19) C
Writing µ next to 14 indicates the mass of a proton/neutron
In this case it is 14 x (1.67 x 10-27) kg
Note: Both of the values for µ and e will be given in exam
Radioactivity:
The random and spontaneous decay of unstable nuclei releasing β-, β+, γ and 4µ2e α
radiations.
Writing the words ‘random’ and ‘spontaneous’ are very important.
Random:
Each unstable nucleus has an equally likely probability of decaying.
For example, we do not know, out of these 5, which will decay when.
, This phenomenon is experienced by fluctuations in the readings.
If a graph is plotted about number of nuclei decaying, it would look
something like this.
Spontaneous:
The rate of decay is not affected by external factors.
Example: Changing temperature, pressure etc.
This can be experienced by no change due to change in temperature/pressure or
any other external factor.
Half Life:
The time required for the initial rate of decay to become half of its original value.
n = 120s
Initial decay= 1024
Final decay = 16
Time passed = ?
n passed = ?
Initial decay * 1/2half lives = Final decay
1024 * 1/2half lives = 16
= 2half lives
64 = 2half lives
