Radioactivity Flashcards
(33 cards)
Thompsons plum pudding model
Electrons, negative
Positive something, make overall charge neutral
Rutherford
Alpha particle
Similar helium particles
Positively charged
Rutherford
Evacuated air
No other particles can disrupt the results
Rutherford
Gold foil
Fine gold sheet
Only few atoms thick
Too thick, alpha absorbed
Rutherford
Zinc sulphide screen
When hit by a charged particle, it gives off a photon of visible light
Can see when microscope lens hit with it
Rutherford results
Most alpha went through foil without deflection
Some deflected slightly
A few bounced back
Conclusion from Rutherford
Majority of particle is empty space, no deflection
Charged alpha particle direction changes by charge of nucleus which is positive
Backscattered, nucleus is very small, positive, high charge density
Ionisation
Result of an atom reacting with a radioactive particle which becomes and ion
Alpha decay
When nucleus of radioactive isotope emits 2p, 2n
New element formed
Beta decay
Neutron in nucleus turns into a p and releases an e
Gamma decay
Gamma radiation released during decay reactions
Radiation
Used in medical places
Tiny amounts of gamma is safe
Too much ionisation causes cell mutations
Penetrative power
a, thin paper
b, few mm of aluminium
y, lead
Deviation in magnetic field
a, South Pole
b, North Pole
y, no deviation
Detection of radioactive particles
Geiger muller tube
Cloud chamber
Photographic film
Protection from radiation
Lead lined apron Lead glass mirror Wearing gloves Remote handling Reduce exposure time
Dangers outside the body
b y, penetrate skin muscle
a, less likely to reach healthy cells
Dangers inside the body
a, high ionising and absorption by cells
b y, less ionising, can escape
Uses of alpha
Smoke alarms
Smoke particles ionised by alpha, alpha count goes down
Uses of beta
Paper thickness checker
Too thin, too many pass
Too thick, not enough pass
Uses of gamma
Crack detection in pipes
Tracers in medicine
Destroy cancerous cells
Irradiate fruit and surgical tools
Gamma has low ionising power, tumour receives a high dose of gamma that can kill cancerous tissue
Scalpels gamma radiated to remove bacteria
Background radiation
Cosmic rays from space
Food
Gypsum, rocks, walls
Radioactive decay
Random
No influence on other nuclei around it
Half life
Average time taken for the number of nuclei of the isotope in the sample to half
Measured in Bq
