Physics - Putting Radiation To Use


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  • Created by: Elliza
  • Created on: 04-06-11 08:57

Ionising - Types of Radiation

Ionising is when an atom either loses or gains electrons. There are three types of ionising radiation

There is a pattern - the more penetrating a form of radiation is, the less ionising it is. This is because it has given off all it's kinetic energy quickly, therefore, there's less left to ionise (knock electrons off) 

Alpha Particles are Helium Nuclei

  • They are big and heavy
  • Their big mass and charge make them strongly ionising
  • They are not very penetrating
  • They are stopped easily (skin stops them)
  • They are used in smoke alarms 
  • They have a positive charge

Beta Particles are Electrons

  • They are in the middle of alpha and gamma concerning their properties.
  • They are negatively charged
  • They are quite small
  • They are moderately ionising and penetrating, (aluminium stops them)
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Ionising - Types of Radiation Continued

Gamma Rays very short wavelength Electromagnetic Waves

  • They are very penetrating (thick lead or concrete will stop them) 
  • They are not very ionising 
  • Although they can get through most things, they will eventually damage something.
  • They can be used to sterilise food.

Gamma Rays and X-rays are pretty similar - however, the way they are produced is different. X-rays are produced manually by launching atoms at metal however, gamma rays are released from unstable atomic nuclei when they decay.

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Background Radiation

Radiation is all around us and most of the time, we don't even know it.

Background radiation can come from:

  • Naturally unstable isotopes all around us - in food, in the air, in building materials and in rocks beneath our feet. 
  • From Space - known as cosmic rays. They come mostly from the Sun. Luckily, the atmosphere protects us from most of these rays. The Earth's magnetic field also deflects cosmic rays
  • Radiation due to human activity, e.g dumped nucleur waste. However, this makes up only 1% of the total background radiation.

The Level of Background Radiation depends on where you are. It is highest at:

  • High altitudes. Pilots are actually more at risk from certain types of cancer because they are closer to the cosmic rays a lot of the time
  • Underground in mines. Minors are surrounded by rocks a lot of the time
  • Certain understand ground rocks (e.g granite) can cause higher levels on the surface, especially if they release radon gas. Radon gas gets trapped inside people's houses.
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Radon Gas

1) Radon concentration in people's houses varies widely across the UK, depending on what type of rock the house is built on.

2) Studies have shown that exposure to high doses of it can cause lung cancer.

3) Evidence suggests that the risk of developing lung cancer from radon is much greater for smokers compared to non smokers.

4) Some medical professionals reckon that about 1 in 20 deaths from lung cancer are caused by radon exposure.

5) New houses where there is a lot of radon exposure must be built with good ventilation systems. These reduce the amount of radon that gets trapped inside the house. 

6) In existing houses, the Government recommends that ventilation systems are put in wherever the radon concentration is higher than a certain level.

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Half Life

The radioactivity of a Sample always decreases over time

The problem with trying to measure the half life is that the acitivity never reaches zero, so we have to use the idea of half life to measure how quickly the activity drops off.

Half life is the time taken the half of the radioactive atoms to decay

A short half life means the activity falls quickly, because lots of nuclei decay quickly. 

A long half life means the activity falls slowly, because most of the nuclei don't decay for a long time.

To work out the half life of something, half it's initial count until you get to the figure mentioned, and then work out the time interval in between each half life.


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