industry

• An emitter is placed on one side of a sheet and a

  detector on the other.

  
• If the thickness of the sheet remains constant the

  activity will not change.
• The source should have a long half-life so that the count rate remains almost

  constant each day and so that it does not need to be replaced too frequently.

  
• Radioactive isotopes are used in industry to

  control the thickness of metal or paper as it is rolled into thin sheet.

  
• If the thickness of the sheet remains constant the 


  activity will not change

  A) aluminium foil

  B) beta emitter

  C) detector

  D) computer

  E) rollers

  F) feedback to rollers

  
• A beta source is used because it can

  penetrate paper or thin aluminium,

  but the amount of penetrating will vary sufficiently as thickness changes

  
• the activity increases or decreases if there is a change

  change in thickness

  
• This can trigger the rollers to squeeze harder or less hard to maintain the correct 
 



  thickness