190  Views  on  Constitution  of  the  Atom.  {^Ap^'iSs"™' 
The  Beta  and  Gamma  Rays. — Another  photograph  was  obtained 
by  Wilson  showing  the  long  range  of  the  electron  expelled  by  in- 
cident gamma  rays.  In  air  at  atmospheric  pressure  this  secondary 
beta  particle  will  traverse  more  than  a  metre.  As  will  be  seen  later, 
the  gamma  rays  are  electromagnetic  disturbances  having  a  minute 
Fig.  3. 
wave-length,  even  compared  with  light  waves,  and  a  correspondingly 
high  frequency.  The  kinetic  energy  is,  as  with  Rontgen  rays  pro- 
pelling electrons,  again  approximately  equal  to  h  times  the  frequency, 
when  h  is  Planck's  constant.    The  mechanism  by  which  these  phe- 
