How do you Tell a Positron From an Electron?

Most recent answer: 01/27/2010

I was wondering about the specific differences between matter and antimatter. How would you tell the difference between a positron and an electron?
- Mike (age 31)
Napavine, WA
There are several ways:
1. Put them between two metal plates connected by a battery.   The electron will be attracted to the positive plate (anode) whereas the positron will be attracted to the negative plate (cathode).
2. Let a beam of them pass through a magnetic field.  A beam of electrons will be deflected one way, the beam of positrons will be deflected the other way.
3.  Put an electron and a positron in with a crowd of electrons.  The electron will shun the other electrons.  A positrons loves electrons. It will be attracted to the nearest one and embrace it. Both will die a miniature annihilation explosion releasing a pair of gamma rays.

Methods 1 and 2 depend on the fact that they have opposite charges and so the electric and magnetic forces on them are opposite.   Method 3 depends on the fact that the positron is an anti-particles of an electron and so can annihilate:
 e- + e+ -->  γ + γ

See:     for some interesting facts.


(published on 01/27/2010)