radioactivity and particles Flashcards
describe alpha radiation
1 particle consists of 2 protons and 2 neutrons (same as a helium nucleus)
charge of 2+
highly ionising
weakly penetrating (blocked by 5cm of air
describe beta radiation
1 particle composed of a fast moving electron
charge of -1
medium ionising effect
medium penetration (blocked by 20cm of air or a sheet of metal
describe gamma radiation
weakly ionising
highly penetrating (blocked by several cm of lead
electromagnetic radiation (no particles)
how can radiation be detected?
photographic film - the film is white as it absorbs radiation it gets darker
geiger muller tubes - they are tubes which transit an electric pulse every time radiation is absorbed, producing a clicking sound
cloud chamber - a container filled with water vapour, ionising radiation causes the vapour to condense, forming tracks
what is background radiation?
the radiation that exists around us all the time
give some sources of background radiation
cosmic rays
radiation from rocks underground
nuclear fallout
some food and drink
medical rays
define half life
the time taken for half the nuclei of a particular isotope in any sample to decay
how is radiation used in sterilisation?
gamma emitters are used to kill bacteria and parasites on equiptment
what are some safety precautions when using radiations?
minimise exposure time
keep as much distance from the source as possible
use shileding eg. lead
what is count rate measured in?
in counts per second or counts per minute
Does the count rate increase or decrease as the detector moves further from the radiation source?
The count rate decreases as the detector moves further from the radiation source
What are the three types of radiation that a nucleus can emit?
alpha
beta
gamma
which type of nuclear radiation is the most ionising?
alpha particles are the most ionising form of nuclear radiation
then its beta and the gamma is the least ionising
what two factors can cause an isotope to be radioactive?
excess of neutrons in the nucleus
the nucleus being too heavy
what are the types of nuclear radiation in order of increasing penetrating power?
Alpha - least penetrating, can be stopped by paper
Beta - can be stopped by a few mm of aluminium
Gamma - most penetrating, can be reduced by a few mm of lead
Which types of nuclear decay cause the isotope to decay into a new element?
An isotope will decay into a new element if the number of protons changes. Therefore, alpha and beta decay will produce a new element.
By what value does the mass number decrease as a result of alpha decay?
the mass number decreasing by 4, because 4 nucleons are emitted.
What is the symbol for activity on a half-life graph?
A
What is the value of the activity of a radioactive sample after two half-lives?
after two half-lives is 1 fourth of its original value.
How does ionising radiation cause cell mutations?
ionising radiation can remove electrons from the atoms that make up DNA
therefore change the structure of the molecule
a structural change in DNA can lead to mutated cells
mutated cells usually either die of get destroyed by the immune system, but some mutation can cause cells to replicate uncontrollably and lead to cancer
how is radioactive waste disposed?
contain it in marked containers
burying it underground
leaving it undisturbed for thousands of years
What would overexposure to nuclear radiation lead to?
radiation poisoning
