Radioactivity Flashcards
what did rutherford’s scattering experiment prove?
the exsistence of the nucleus
what three things were observed during the alpha scattering experiment
most alpha particles passed straight through the foil with no deflection
small amount of particles deflected by a large angle
very few particles were defelected back by more than 90°
describe the plum pudding model
atoms made up of a sphere of positive charge
small areas of negative charge evenly distributed throughout
what are the three types of radiation
Alpha
Beta
Gamma
what are the properties of alpha radiation
range of 2-10cm in air
highly ionising
deflected by magnetic and electric fields
absorbed by paper
what are the properties of beta radiation
range of 1m in air
weakly ionising
deflected by electric and magnetic fields
absorbed by aluminium foil
what are the properties of gamma radiation
infinite range in air follows inverse square law
very weakly ionising
not deflected by electric and magnetic fields
absorbed by a few Km of concrete or few inches of lead
outline an experiment that can be used to detect the three different types of radiation
Using a Geiger-miller tube find the background count when the source is not present
place the source of radiation close to GM tube and measure the count rate
place a sheet of paper if count rate reduces source is emitting alpha radiation repeat with aluminium foil and lead
name three uses of gamma radiation in medicine
As a detector
sterilising medical equipment
in radiation therapy
outline how gamma radiation can be used as a detector
radioactive source with a short half life which emits gamma radiation can be injected into a patient
and the gamma radiation can be detected using gamma cameras in order to help diagnose patients
outline how gamma radiation can be used to sterelise medical equipment
gamma radiation will kill any bacteria present on the equipment
outline how gamma radiation can be used in radiation therapy
gamma radiation can be used to kill cancerous cells in a targeted region of a body such as a tumour however it will also kill all healthy cells in that region
what does gamma radiation do in air as it travels and why does this occur
it spreads out in all directions equally
therefore it obeys an inverse square law
what is half life
the time taken for the mass of a radioactive isotope to decrease to half the intial mass or activity
name four sources of background radiation
radon gas
rocks
cosmic rays
artificial sources
what is the decay constant
the probability of an individual nucleus decaying per second
what is the activity of a radioactive isotope
the number of nuclei of the isotope that disintegrate per second
why is ionising radiation hazardous
as it can damage living cells
how can ionising radiation affect living cells
it can destroy cell membranes
it can damage vital molecules such as DNA by forming free radical ions which react with vital molecules
name 6 examples of ionising radiation
gamma alpha beta neutrons protons x-rays
what does gamma radiation consist of
photons
what is intensity of radiation
the radiation energy per second passing normally through unit area
why does a beam of high energy electrons get diffracted by a target nuclei
as the de broglie wavelength of the electrons is similar to the diameter of the target nucleus
