Waves/Radiation Flashcards
(30 cards)
What are the main particles inside an atom?
Protons, electrons and neutrons
What is ionisation?
The removal or addition of an electron to form a charged (positive or negative) ion.
What is an ion?
An atom that has gained or lost electrons so has either a negative or positive charge.
List three types of ionising radiation.
Alpha particles
Beta particles
Gamma rays.
Describe an alpha particle
It is a helium nucleus with two protons and two neutrons. It has a mass of 4 atomic mass units (amu).
It has a 2+ charge.
Describe a Beta particle.
It is a fast moving electron. It has tiny mass (1/2000 amu).
It has a -1 charge.
Describe Gamma rays
High energy electromagnetic wave
Describe the penetrating power of alpha, beat and gamma radiation
Alpha is the least penetrating it it stopped by a sheet of paper or a few cm of air.
Beta can pass through paper but is stopped by 2-3mm of aluminium.
Gamma rays are the most penetrating only stopped by more than 5cm of lead.
Describe ionising power of alpha, beta and gamma radiation
Alpha is highly ionising, beta less so and gamma radiation is the least ionising of the three.
What is meant by the ‘activity’ of a radioactive source?
The number of nuclei that decay per second
Where does nuclear radiation come from?
The unstable nuclei of atoms called radioisotopes decaying which means giving out radiation to become stable.
In the relationship A=N/t what do each of the letters represent and what units should you use?
A= activity, measured in Becquerels(Bq).
N= number of decays.
t= time(s).
List some sources of background radiation.
Cosmic rays, rocks, soil, living things(plants and animals emit small amounts of radiation).
Why is it important to measure exposure to radiation?
Radiation can kill or damage cells. It causes ionisation which can start chains of dangerous reactions in the body. If it is swallowed or breathed in it can continue to harm the body from the inside.
What is the average background radiation in the U.K?
2.2 mSv
What is the effective dose limit for a mamber of the public?
1mSv
What is the annual effective dose limit for a radiation worker?
20 mSv
What three factors need to be taken into account when deciding the potential harm to a person caused by ionising radiation?
The absorbed dose
The type of radiation
The type of tissue absorbing the radiation.
What is the absorbed dose of radiation?
What units does it have?
What symbol it it given?
The energy absorbed per unit mass of absorbing material.
Its units are Grays (Gy)
The symbol is D.
What is the equivalent dose of radiation? Also give its symbol and units.
A measure of the biological risk caused by radiation.
(absorbed dose * weighting factor)
Its symbol is H.
Its units are Sieverts (Sv)
What is the weighting factor of radiation and what symbol is it given?
It is the number given to each type of radiation relative to its ability to cause biological harm. It is given the symbol WR.
What is the dose equivalent rate and what symbol and units does it have?
It is the rate at which the equivalent dose is received. Its symbol is Ḣ. Units are Svh-1 for hours or years.
Give three different uses of nuclear radiation
Making energy - nuclear power stations.
Medicine - an alpha source can be put close to a tumour to kill the cells.
Industry - used as tracers to follow the path of liquid and detect leaks or blockages.
What is the half-life of a radioactive source?
The time it takes for half its nuclei to decay.
