Question

Draw a schematic arrangement of the Geiger Marsden experiment. How did the scattering of `alpha` particles by a thin foil of gold provide an important way to determine an upper limit on the size of nucleus? Explain briefly.

Answer 1

Both the nucleus and an alpha particle are
positively charged. When an alpha particle
approcaches a nucleus, it is repelled, the velocity
and hence KE of `alpha` particle goes on decreasing.
in turn, potential energy of the system goes on
increasing. At a cartain distance, the entire KE
of `alpha` particlel is converted into P.E. the alpha
particle can no longer go closer to the nucleus.
This distance of closet approach of `alpha` particle
gives us the approxiate size of the nucleus.