Radioactivity

Late 1800's...

1) Röntgen discovers new rays... X-rays
       electron beam strikes a piece of glass,
              the first TV tube
 
 

...a tube like that of electron diffraction 2) Becquerel's experiment:

• cover different elements with opaque wrap
• 
       place on photographic plate
• does something penetrate black coating and
• 
        expose photographic plates???
• yes! uranium, radium, and thorium...
• 
        emit energetic rays without any energy input!
• some elements inherently unstable,
• 
        spontaneously release energy