radioactivity Flashcards
mass number
-total number of particles in the nucleus an atom
atomic number
-the number of protons in an atom
relative mass, charge and location of an electron
1/2000, -1, shell
relative mass, charge and location of a proton
-0, +1, nucleus
relative mass, charge and location of a nucleus
1, 0, nucleus
what is nuclear radiation(ionising radiation)
-causes ionising radiation by bashing into atoms and knocking electrons off them
-these atoms then become ions
how is ionising radiation detected
-by a Geiger-Muller tube
relationship between distance radiation penetrates before hitting an atom and ionising amount
-the further radiation travels before hitting an atom, the less ionising it is
three types of ionising radiations
-alpha particles
-beta particles
-gamma rays
what is radioactive decay
-nuclei are unstable and radioactive due to imbalance of protons or neutrons in the nucleus
-nuclei emits radiation to become more stable
-these changes are spontaneous and random
features of alpha particles
-made up of 2 protons and 2 (4-He) neutrons(big and slow)
-low penetrating power
-high ionising power
-electrically charged(+), are deflected by electric and magnetic fields
-stopped by thick paper
-range in air:5cm
features of beta particles
-an electron(emitted from the nucleus of an atom when a neutron turns into a proton and an electron)
-medium penetrating power
-medium ionising power
-electrically charged(-), are deflected by electric and magnetic fields
-stopped by aluminium sheet
-range in air:1m
gamma rays
-rays of energy(EM wave), no mass
-high penetrating power
-low ionising power
-no charge
-stopped by thick lead
-infinite range in air
isotope
-an atom of the same element that have an equal number of protons but a different number of neutrons
method of investigating penetrating powers of different types of radiation
- connect Geiger-Muller tube to the counter and measure background radiation over one minute without any sources present
- repeat three times and take an average. Subtract this value for all subsequent readings
- place radioactive source a fixed distance of 3cm away from the tube and take another reading of count rate over a period of one minute
take a set of absorbers, with different thicknesses - one at a time, place these absorbers between the source and the tube and take another reading of count rate over a period of one minute
- repeat for other radioactive sources
check equations from book
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neutron emission
-some isotopes can decay by emitting neutrons
how does a Geiger muller tube work
-transmits an electrical pulse to a counting machine each time it absorbs radiation
-this makes a clicking sound/displays the count rate
-the greater the frequency of click/the higher the count rate, the more radiation the Geiger Muller tube is absorbing
natural sources of background radiation
-Radon gas from rocks and buildings
-Cosmic rays from space
-carbon-14 in biological material
-radioactive material in food and drink
artificial sources of background radiation
-nuclear medicine
-nuclear waste
-nuclear fallout from nuclear weapons
-nuclear accidents
why does radon gas from rocks and buildings cause radiation
-airborne radon gas comes from rocks in the ground and building materials
-this is due to the presence of radioactive elements, such as uranium,, which occurs naturally in small around of all rocks and soils
why does cosmic rays from space cause radiation
-sun emits enormous number of protons every second
-some protons enter the Earth’s atmosphere at high speeds
-when they collide with molecules in the air, this leads to production of gamma rays
how does carbon-14 of biological material cause radiation
-all organic matter contains a tiny amount of carbon-14
-living plants and animals constantly replace the supply of carbon in their systems hence the amount of carbon-14 in the system stays almost constant
how does radioactive material food and drink cause radiation
-naturally occuring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elemtns
-some foods contains higher amounts such as potassium-40 in bananas
-radioactive material in food is still minuscule and is not a cause for concern
how does nuclear medicine cause radiation
-nuclear radiation is used in medicine (X-rays, CT scans, etc)
nuclear waste
-causes nuclear radiation
-dangerous to people handling it
nucelar fallout from nuclear weapons
-fallout is the residue radioactiv ematerial that is thrown into the air after a nuclear expolision
how does nuclear accidents cause radiation
-contributes a large dose of radiation to the environment
what is the activity of a radioactive source
-the rate at which the unstable nuclei decay(measured in Becquerels Bq)
1 Bq = 1 nucleus in the source decaying in 1 second
how does activity of a radioactive source vary with time
-activit decreases with time as each decay event reduces the overall number of radioactive particles in the source
wyh do fluctuations occur in a graph of count rate against time
-due to the randomness of radioactive decay
define half life
-the time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half
how to measure half life
-measure the initial activity of the sample
-determine the half-life if the original activity
-measure how the activity changes with time
-the time taken for the activity to decrease to half its original value is the half-life
uses of radioactivity
-monitoring thickness of materials
-smoke detectors
-medical procedures
-sterilising food
-sterilising medical equipment
-determining age of ancient artefacts
how are smoke detectors used by radiation
-alpha particles are used in smoke detectors
-alpha radiation will normally ionise the air within the detectors, creating a current
-the alpha emitter is blocked when smoke enters the detectors
-the alarm is triggered by a microchip when the sensor no longer detects alpha
how can the thickness of materials be measured using radiation
-when a material moves above a beta source, some beta particles will be absorbed, but most will penetrate
-the amount of beta particles passing through the material can be monitored using a detector
-if the material gets thicker, more particles will be absorbed and the count rate decreases, and vice versa
how can radiation be used in the diagnosis and treatment of cancer
-ionising radiation can kill living cells, some cells are more susceptible to radiation than others
-beams of gamma rays are directed at the cancerous tumour, they can penetrate the body and reach the tumour
-beams are moved around to minimise harm to healthy tissue whilst still begin aimed at the tumour
how can food and medical equipment be sterilised using radiation
-gamma radiation can be used to sterilise medical equipment
-food can be irradiated in order to kill any microorganisms
-gamma rays are the most penetrating, so can irradiate all sides of instruments
contamination
-the accidental transfer or a radioactive substance onto or into a material
what can contamination cause
-small amounts of an isotope in contaminated areas will emit radiation and the material becomes radioactive
irradiation
-the process of exposing a material to ionising radiation
what can irradiation cause
-can kill living cells
-will not make it radioactive
how can radiation affect humans
-radiation can mutate DNA in cells and cause cancer through both irradiation and contamination
how can contamination affect humans
-if a radioactive source gets inside the human body(inhaling or ingesting)
-internal organs will be irradiated as source emits radiation as it moves through the body
how to prevent irradiation
-shielding to absorb radiation
-lead-lined suits are used to reduce irradiation for people working with radioactive materials
how to prevent contamination
-an airtight suit is worn by people working in an area where a radioactive source may be present
How does ionising radiation lead to mutations
-ionising radiation causes damage to DNA
-the cell can sometimes successfully repair the DNA
-incorrect repairs can cause a mutation
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what types of radiation is more dangerous outside the body and why
-highly ionising(alpha)
-likely to cause most harm to living cells inside the body
what types of radiation is more dangerous from outside the body
-highly penetrating(gamma)
-they can pass through the skin and reach living cells in the body
nuclear fusion
two small nuclei join together to produce a larger nucleus
where does nuclear fusion happen
in stars, conditions are not right for earth
nuclear fission
splitting of a large, unstable nucleus into two smaller nuclei
chainr eaction
neutron emitted from the splitting of a nucleus causes further nuclei to split and the neutrons emitted from these cause further fission reactions
control rods
made of a material which absorbs neutrons without becoming dangerously unstable themselves
moderator
slows down nuetrons
requirements of fusion to happen
very high temperatures and very high pressures
requirements of nuclear fission to happen
thermal neutrons to induce fission
