P6 - Radioactivity Flashcards
Mass of an electron
0.0005
Overall all charge of a nucleus is
Positive
What are alpha particles
-> the nucleus of a helium atom
What are beta particles
-> fast moving electrons
What are gamma waves
A type of Em wave
What is a neutron
A particle found in the nucleus
Chemical symbol of alpha particles
⁴₂He
Chemical symbol of beta particle
0
ß
-1
Gamma wave chemical symbol
0
Y
0
What is different about gamma wave compared to alpha and beta particles
Has no mass nor charge
This is because it is an Em wave
Chemical symbol on neutron
1
n
0
Why do particles decay
Because they have an unstable nucleus
The neutrons are not stable
What does a neutron from when it is unstable
Forms a proton and a beta particle
How do you record radiation
Use a Geiger-Müller counter
How does a Geiger-Müller counter work
The clicks heard are small currents produced when the radiation ionises the gas inside the tube
Order of penetration in alpha, beta and gamma
Least penetrating - alpha particles
Medium - beta particles
Most penetrating - gamma waves
Order of ionisation alpha, beta and gamma
Least ionising - gamma
Medium - beta
Most ionising - alpha particles
How can you stop alpha particles
Using a few sheets of paper
How can you stop beta particles
Using a few mm of aluminium
How do you stop gamma radiation
Buy using lead or a few m of concrete
However some still passes through
Why is an alpha particle the most ionising
-> to ionise an atom, energy has to be transferred to it
-> alpha particles are able transfer more energy as they travel through the atom
-> which is also why they have a shorter range as the energy is used to ionise the atom
What is radioactive activity
The radiation emitted from a radioactive substance every second
What is activity measured jn
Becquerels
What is half life
Time taken for activity to half
AND
time taken for unstable nuclei to decay
What is contamination
-> occurs when radiation is taken INSIDE the body
-> internal contamination CANNOT be removed
What is irradiation
-> occurs when radioactive material is OUTSIDE the body
-> radiation can travel into the body
What are medical tracers
-> Radioactive isotope that is inhaled, swallowed or injected
How does medical tracers work
The radioactive isotope is flame into the body
The different organs absorb different amounts of the radiation
The gamma camera is used to detect the radiation to show problems
What is a gamma knife
Can be used to treat cancer
Movable source of gamma radiation that moves around the body
How does a gamma knife work
It’s a movable source of gamma radiation
High dose is given to the tumour
Low doses given to healthy cells, because it is moving
Main sauces of background radiation
-> food and drink
-> radon gas (rocks)
-> ground and buildings
-> cosmic rays
-> artificial sources
-> medical uses
Give two reasons why there are a wide range of results around the count rate in an experiment measuring radioactivity
- radioactive decay is random
- background radiation may influence results
Why is it better to use a longer time interval when measuring count rate
-> less variation in count rate
-> can give average count rate
Why is an element with a low half dangerous
Means it decays faster, and also has a higher activity
