WJEC P2 Radioactivity

Alpha Particles!

• Are Helium Nuclei. Mass 4, Charge +2, 2 protons and 2 neutrons.
  
• Big, Heavy and slow moving.
• Don't penetrate - stopped by paper -Not harmful to us.
• Strongly ionising. (because of their size they bash into each other and knock electrons off, before slowing down)

Beta Particles!

• Are Electrons. no mass, and charge -1  Inbetween Gamma and Alpha
• Quite fast and small.
• penetrate moderateley - stopped by Alluminium - Can get into the body.
  
• Moderateley ionising

Gamma Rays!

• Very short wavelength - EM waves
• Penetrate a long way - stopped by lead - Get into body, harmful, can damage cells and cause cancer.
• Weakly ionising - they pass through rather than collide.
  

Definition - How long it takes for half of the Radioactive atoms to Decay.

Simple Half Life Question -

The activity of a Radioisotope is 640 cpm. 2 hours later it has fallen to 40 cpm. Find the half life of the sample.

Initial Count  -  1 half life  -  2 half lives  -  3 half lives  -  4 half lives

        640  -   /2  -  320  -  /2  -    160    -  /2  -    80    -  /2   -   40

It take 4 half lives for it to reach 40 cpm. So 2 hours represents 4 half lives. The half life is 30 mins.

Using a graph -

Subtract the background radiation, count rate on Y-axis and time in hours on X-axis. Plot your curve. Half the first countrate and draw across till it meets your curve, now draw down to your X-axis. This is your half life. Continue to half the countrate to continue halfing.

Definition - Very low levels of radiation that we are constantly exposed to.

Background Radiation changes depending on where you are. -

• Hight Altitude - It increases ( exposure to Cosmic Rays)
• Underground - It increases ( mines because of all the rocks)
• Underground rocks can cause an increase on the surface.
  

Background Radiation comes from many sources -

• The ground - 7%
  
• Granite rock - 7%
  
• food and drink - 12%
  
• Cosmic Rays from space - 10%
  
• Medical (X-rays, sterilising...) - 12%
• Radon Gas - 51%
• Nuclear Industry - 1%
  

Radon Concentration varies across the UK- depending on what rocks your house is built on either Ingneous or Sedimentary

High Doses = Lung Cancer, it breaks down cells.  1 in 2 deaths per year from Lung cancer are because of Radon Gas.

It Rises through the soil - gets into your HOUSE! If Radon Gas gets into your house you need -

• good ventilation.
• Seal cracks
•  can buy a Radon Pump

New Houses must be designed with Good Ventilation.