Below is an image of Potassium-40 undergoing Beta+/- decay. Beta Radiation!!! Beta radiation is the ejection of energetic electrons and anti-electrons (called positrons) from an atom. These electrons and positrons are moving with incredible force. They smash into our bodies and may cause harm. Beta radiation is one of the largest sources of radiation humans are exposed to. You Eat This Each Day!!! This atom is Potassium-40, a radioactive version of the Potassium you and I eat each day in our bananas and vitamins. When you eat light salt or Potassium salt, you are eating Potassium Chloride, mostly, which contains small amounts of K-40, radioactive Potassium! Yum! Beta radiation is stopped by thin metal easily, a sheet of aluminum being the most often cited method. Student - "So... electrons flow down a wire to make electricity, which powers my computer, etc?" Teacher - "Sure! They also kill you when you're blasted by massive amounts of them... beta radiation." Student - "But... what's the difference??? Will a 9Volt battery kill me???" Teacher - "Electricity is electrons peaceably moving between one atom to the next as a field of energy." Teacher - "Beta radiation is electrons running free at high speed, like tiny bullets! You are quite safe." Student - "You wrote above that bananas have beta radiation... are they deadly?" Teacher - "No... K-40, a natural beta emitter, produce much of the radiation in the human body, normally." Teacher - "This is safe and some scientists even think tiny bits of radiation jump start you're bodies natural defenses..." Student - "! WOW ! That is crazy talk!!!"