alpha

• alpha particles have an

  unstable nucleus
• alpha radiation is when a nucleus loses

  2 protons and 2 neutrons

  
• alpha radiation has what charge

  positive

  
• alpha radiation is the

  biggest

  slowest

  
• alpha radiation is the most ionising

  
• alpha radiation is stopped by

  paper

  skin

  aluminum

  
• alpha radiation has a range of

  5 centimeters
• what is the penetration of alpha radiation

  least penetrating
• alpha radiation is the same as the nucleus of

  helium

  
• One type of smoke detector uses Americium-241, an alpha particle source, to detect smoke.

  
• The alpha particles pass between the two charged metal plates, causing air particles to ionise (split into positive and negative ions).

  
• How does a smoke detector work ?

  • THE radioactive source is  americium-241.

  this is an alpha emitter.

  • This ionise the molecules of the air forming ions and electrons which are attracted to a pair of charged plates 
  • When the ions and electrons hit the plates they provide a small amount of electricity (a small current)
  • This current stays constant and is monitored by the smoke alarm.

  
• WHAT HAPPENS WHEN SMOKE ENTERS THE SMOKE DETECTOR

  • the smoke particles near to the radioactive source absorb many of the alpha particles.
  • The number of ions and electrons between the charged plates therefore decreases.
  •  the current which is passed between the charged plates also decreases.
  • the smoke detector detector notices the the decrease in current and sets off the alarm
• the smoke alarm would not work with a radiation source that emits gamma or beta .explain why?

  gamma and beta will penetrate smoke

  no change in the count rate would be detected

  
• why is it safe to use a source of alpha radiation in a smoke detector?

  it has a range of 5 centimeters

  so it is going to be contained in the smoke alarm.

  it is the least penetrating

  
• why does the smoke alarm go off

  the smoke particles stop the radiation source from reaching the the alarm circuit, this triggers the circuit