Physics for the IB MYP 4&5: by Concept 5.11
Radio Activity, Half Life and
Nuclear Reaction
Hodder & Stoughton © Paul Morris 2015
Learning Objectives
- Identifying Radio activity
- Determine the half life of a Nuclear reaction
Radioactivity
All the element having atomic number greater
than 82 emit invisible radiation all the time.
The phenomenon of emission of these
powerful rays is called Natural Radioactivity
and the element that emit such is called
‘Radioactive element’.
https://www.youtube.com/watch?v=UtZw9jfIxXM
Types of Radioactive Rays
There are three types of radioactive rays:
Alpha (α)
Helium nucleus
Beta (β)
Electro
n
(γ)
Gamma
High-energy
photon
4
2 He
0e
-1
- paper
- Lead
- concrete
Alpha radiation
It is actually the nucleus of a helium
atom
consisting of 2 protons and 2 neutrons, held
tightly together.
It comes directly from the nucleus, so only
big atoms tend to emit it.
It strongly interacts with matter around
it, smashing past atoms and ionising them.
Beta radiation
It a high speed electron, give off when a
neutron turns into a proton
They are many times smaller than the
alpha radiation.
They interact much less strongly with matter.
Beta radiation (a high speed
electron).
Gamma radiation
Sometimes a nucleus that is still unstable
after a beta or beta or alpha decay.
This is an electromagnetic wave with a
very short wavelength.
It does not change the number of protons
or
neutrons in the nucleus.
Gamma radiation (a short
electromagnetic
wave).
Radioactive decay
The decay process is random.
No one can predict when 1 nucleus
decays.
The emission is spontaneous.
It is possible to make a statistic
prediction.
The danger of radiation sources-outside
of the body
Betas and gammas are the most dangerous.
They can penetrate and reach the cells
of organs.
They are absorbed and ionise the cells.
This can cause cancer.
Alphas are the least dangerous.
Nuclear bomb
• The gamma ray they emit can travel king
distances without absorption.
Radiation burn
• This has been caused by long exposure to
gamma rays.
The danger of radiation sources- inside
the body
• Alpha radiation is the most dangerous as it is
strong absorbed and ionizes cells.
• Betas and gammas are not strongly absorbed
and cause less ionization damage.
Killing cells using gamma radiation
• Gamma rays are used to kill cancer cells and
bacteria.
Other uses of radiation
•
•
•
•
Electricity generation.
Sterilization of hospital equipment.
Checking leaks in pipes.
Irradiation of food.
Half- life
It is time required to reduce half of its original
activity.
• Useful isotope list with half life:
1. Manganese -56
- 2.58 hours
2. Sodium- 24
- 15 hours
3. Phosphorus -32
- 14.3 days
4. Zink – 65
- 245 days
5. Sulphur- 35
- 87.1 days
6. Cobalt- 60
- 5.25 yrs
7. Iron- 55
- 2.94 yrs
Nuclear reaction
Nuclear reaction three types :
1.Fission: fission is a process in which a heavy
nuclear is divided into two piece. A typical
enable is the fission of uranium.
2.Activation: Activation involves the capture of
neutron with the subsequent emission of
radiation.
3.Transmutation: Transmutation is process in
which one element is converted to another
element.