WJEC P2 Radioactivity

Basic facts about the different area's of radioactivity needed for the P2 paper for WJEC.

HideShow resource information
  • Created by: Rosie
  • Created on: 25-05-11 17:16

Radioactive Particles

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.
1 of 4

Half Life

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.



2 of 4

Background Radiation

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%
3 of 4

Radon Gas

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.


4 of 4

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Radioactivity resources »