Physics paper 1

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What is radioactive decay?
unstable isotopes decay into other elements and give out radiation as they try and become more stable
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What are types of ionsing radiation?
alpha,beta,gamma or neutrons
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What is alpha radiation?
when an alpha particle is emitted from the nucleus
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What is an alpha particle made from?
two neutrons and two protons
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Why are they strongly ionising?
because of their size
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What is a beta minus particle?
a fast moving electron released by the nucleus, they have no mas and have relative charge of -1
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What is a beta plus particle?
a fast moving positron, exactly the same mass as an electron but a +1 charge
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Beta minus particles have a range in air of...
a few metres
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Beta plus particles have a...
smaller range in air
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What is annihilation?
when a positron hits an electron it produces gamma rays
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After a nucleus has decayed it often undergoes...
nuclear rearrangemnt and releases energy
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What are gamma rays?
waves of em radiation that are released by the nucleus that carries energy
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Gamma rays travel over...
long distances in air
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What does alpha decay do to the charge and mass of the nucleus?
it decreases the charge and mass
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How many protons and neutrons are lost during alpha decay?
two protons and two neutrons
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What does beta minus decay do to the charge of the nucleus?
it increases it
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What happens during beta minus decay?
a neutron changes into a proton and an electron , mass doesnt change atomic number increases by 1
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What happens during beta plus decay?
a proton changes into a neutron and a positron, mass number doesnt change and atomic number decreases by1
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What happens during neutron emission?
nucleus emits a proton, mass decreases by 1 atom number stays the same
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What are gamma rays used for?
removing excess energy from an atom
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What happens to the nucleus when a gamma ray is emitted?
it goes from excited to more stable, mass and atomic number stay the same
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What is activity?
the rate at which a source decays
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What is activity measure in?
becquerels Bq (Bq is 1 decay per second)
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What can activity be measured using?
a geiger-muller tube, clicks everytime it detects radiation
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The more radiation photographic film is exposed to...
the darker it is
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Each time a radioactive source decays...
one more radiactive nucleus disappears
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As the unstable nuclei steadily disappear...
the activity as a whole decreases
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What is half life?
the average time taken for the number of radioactive nuclei in an isotope to halve
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Short half life means...
activity falls quickly because the nuclei are very unstable and rapidly decay
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Why are sources with a short half life dangerous?
the high amount of radiation they emit at the start, they quickly become stable
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Long half life means....
activity falls more slowly,because most of the nuclei don't decay for a long time
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Why are long half lives dangerous?
because the source sits there for millions of years releasing small amounts of radiation
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Two hours is...
4 half lives
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What is background radiation?
low level radiation that's around us all the time
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What does background radiation come from?
radioactivity of naturally occurring unstable isotopes, radiation from space (cosmic rays), radiation due to human activity eg nuclear waste
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What is the absorbed radiation dose?
the amount of radiation your body absorbs
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What is irradiation?
exposure to radiation
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What is contamination?
when radioactive particles get onto objects
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If contaminated particles decay they...
release radiation which harms you
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What do lower doses of radiation cause?
doesn't kill cells, causes mutations, divide uncontrollably into cancer
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What do high doses of radiation cause?
radiation sickness
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Outside the body what radiation is most dangerous?
beta and gamma, because they can penetrate the body and get delicate organs
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Inside the body what radiation is the most dangerous?
alpha radiation because it is strongly ionsing meaning contamination
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If two sources produce the same type of radiation and start of with the same activity the one with the longer half life is....
more dangerous, because the activity slows more gradually
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How do smoke alarms work?
a weak alpha source is in smoke alarms,close to two electrodes,the source causes ionisation and current flows, smokes absorbs radiation and current stops
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What is nuclear fission?
the splitting up of a big atomic nuclei which releases energy
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What is nuclear fusion?
the joining of two small nuclei at high speeds to create a larger heavier nuclei
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Husion only happens at...
high temperature and pressure
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Why does it need high pressure and temperature?
because the strong force due to electrostatic repulsion has to be overcome
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The products of nuclear fusion have...
very long half lives
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Order of the planets?
mercury,venus,earth,mars.jupiter,saturn,uranus,neptune
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What are asteroids?
lumps of rock and metals that orbit the sun found in asteroid belt
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What are comets?
lumps of ice and dust that orbit the sun
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What is the steadystate theory?
the universe has always existed as it is now, and it will always do
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What is the big bang theory?
all the matter in the universe occupied a very small space which was very dense and got hot and caused an explosion
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Other cards in this set

Card 2

Front

What are types of ionsing radiation?

Back

alpha,beta,gamma or neutrons

Card 3

Front

What is alpha radiation?

Back

Preview of the front of card 3

Card 4

Front

What is an alpha particle made from?

Back

Preview of the front of card 4

Card 5

Front

Why are they strongly ionising?

Back

Preview of the front of card 5
View more cards

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