How were radioactive materials discovered?
Henri Becquerel used covered
Photographic plates that were placed
under Uranium salts to discover
radioactivity.
Henri Becquerels work was expanded
On by Marie and pierre curie
Who investigated and discovered
a range of new radio active elements.
What is background radiation?
Radiation which is present all around in the environment
Give three sources of background radiation
- rocks
- cosmic rays from space
- food i.e. banana
What is radiation?
Radiation is the emission of energy as electromagnetic waves or as moving subatomic particles
What are the 3 types of radiation
Alpha
Beta
Gamma
What is radioactivity?
Unstable nuclei are at the heart of radioactivity they are unstable due to: too many protons, too many neutrons or too large. To become stable the nucleus releases energy through radioactivity
What was the history of the model of the atom?
-Back in ancient Greece philosophers came up with the idea of everything being made up of tiny indivisible particles they called atoms
- after the discovery of the electron as being a subatomic particle in atoms. J.J. Thompson came up with the plum pudding model of the atom in 1904. Electrons buried inside the atom which is made from positively charged material
What is an isotope?
An isotope is an atom with the same number of protons and electrons but different number of neutrons.
What is a radioisotope?
A radioisotope is an isotope that is radioactive e.g. carbon 14
What is alpha radiation and decay?
An atom decays into a new atom and emits an alpha particle (2 protons and 2 neutrons)
Alpha radiation is the nucleus of a helium atom travelling at extremely high speeds
What is beta radiation and decay?
Beta- an atom decays into a new atom by changing a neutron into a proton and electron
The fast moving high energy electron is called a beta particle.
What is gamma radiation and decay?
Gamma after alpha or beta decay surplus energy is sometimes emitted. The atom itself is not changed.
Gamma radiation is part of the EM spectrum a wave with a very high frequency very short wavelength
What is ionising power?
Ionising power is the ability for nuclear radiation to remove electrons from atoms to form ions
What is alpha radiations:
Symbol
Range in air
Stopped by
Ionising ability
Symbol: a
Range in air: can travel up to 5cm until they collide with air particles
Stopped by: a sheet of paper
Ionising ability: very strong
What is beta radiations:
Symbol
Range in air
Stopped by
Ionisng ability
Symbol: B
Range in air: can travel up to 1m
Stopped by: a few millimetres of aluminium
Ionising ability: quite strong
What is gamma radiations:
Symbol
Range in air
Stopped by
Ionising ability
Symbol: Y
Range in air: can be unlimited
Stopped by: lead several cm or concrete 1m
Ionising ability: weak
Why is gamma radiation not suitable for monitoring the thickness of foil and smoke alarms?
Alpha radiation is used for smoke alarms
beta and gamma are too penetrating and it needs a charge and gamma does not have a charge
Beta is used for the thickness of paper or foil because alpha is stopped by paper and gamma would pass straight through without being affected
What is activity (radioactive)?
The activity of a radioactive source is the number of unstable nuclei that decays every second
What is count rate?
The number of decays recorded each second by a detector (e.g. geiger - muller tube)
What is a half life
Half life is the time taken for half of the atoms in a sample to decay
What is the calculation for half lives
Count rate after n half lives = count rate before/2^n
What are radioactive tracers?
Radioactive elements injected into patients in order to image and diagnose a range of illnesses
What are gamma cameras?
The half life should be long enough to make sure we can get a good image but mostly decayed soon after
What is gamma beam therapy?
Treating cancer with targeted gamma ray beams
