2nd step
: 01 : : 02
: : 03 : : 04 : : 05
: : 06 : : 07 : : 08
: : 09 : : 10 :
Finding collisions
Beam particles whose tracks do NOT remain parallel all the way through
the picture must have interacted with a proton in a hydrogen atom. The
arrowed tracks have interacted where the highlighted lines stop (move
cursor 
over the picture)
In a real experiment both these collisions would have been recorded and
analysed. Here we will concentrate on the more interesting 'event' that
produces a spray of 4 charged particles.