Radiation revision

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  • Created on: 15-05-14 18:30
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Atomic Relative Relative
Radiat ion particle mass charge
Atoms Proton 1 +1
- Atoms have a small nucleus surrounded by electrons in shells
- Isotopes have a different number of neutrons Neutron 1 0
- The nucleus of an unstable isotope will decay by giving out
Electron 1/1836 -1
(alpha), (beta) or (gamma) radiation
Radiation type What it consists of Where it comes from
Alpha Helium nucleus 2 protons, 2 neutrons (nucleus)
Beta Fast-moving electron Neutron (nucleus)
Gamma Electromagnetic radiation Nucleus
Alpha decay
(Make sure mass numbers and proton
numbers on both sides add up)
Beta decay
- Neutron disintegrates into a proton and electron
Gamma decay
- Wave with short wavelength
- When a nucleus emits it, it doesn't lose mass, just energy
Unstable isotopes
- Strong nuclear force holds nucleons together
- Electric force causes protons to repel each other
- Too many or too few neutrons unstable nucleus particles from original nucleus break off
- more stable nucleus
- Radioactive decay is random (=can't predict which nucleus decays next/when)
- Ionising radiation can knock an electron out of an atom (making it an ion)
- In atoms of DNA, this can cause mutations, which can cause cancer

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Background radiation
- = low level radiation from our environment
- Sources: radon gas, granite, cosmic rays, bricks in buildings
- Detected with count meter attached to Geiger-Müller tube, in counts per minute (cpm)
Radiation badge
- Contains photographic film- when developed, blackens to show amount of radiation absorbed
- Useful, but levels of irradiation may differ on different body parts + provide no indication of
whether radioactivity comes from within worker
- Film is in light-proof packet so it doesn't blacken from light
Just…read more

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Nuclear power
How nuclear fission works
- Neutrons fired at U-235 or plutonium
- Uranium nucleus absorbs neutron to become U-236 briefly
- Nucleus then splits into 2 daughter nuclei (kryptonium and barium) + gives out 3 more neutrons
+ kinetic energy + gamma radiation
- 3 neutrons hit other nuclei more fission chain reaction (if uncontrolled, can cause nuclear
- Nuclear waste is radioactive so harmful (can cause mutations cancer). It lasts for a long
time.…read more

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We can work out how long ago something died by comparing the amount of C-14 left in it to
how much would be in a similar living object
- Problems:
- Unsuitable for materials older than 50,000 years as the levels of C-14 are not
detectable above the activity of background radiation
- Only works for things which were once living
- E.g. 120kg of wood has a radioactivity of 24Bq (corrected for the background radiation).…read more

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Effect on cells
- Low radiation dose: may have no lasting effect
- Higher radiation dose: may cause mutations to occur cancer
- Very high radiation dose: can kill living cells. Can be used to kill cancer cells
- Radiographers are protected with lead-lined suits
Models of t he atom
Plum pudding model by J.J. Thompson Geiger and Marsden's experiment
Alpha particle fired at thin gold foil.…read more


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