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?

Answer 1

The Schematic arrangement of Geiger-Marsdon Experiment (also known as Rutherford Scattering Experiment) is shown in fig.



Observations: (i) Only a small fraction of number  of α-particles rebound back. This  shows that the number of α-particles undergoing head on collision is very small. The conclusion is that the entire positive charge of atom is concentrated in a small volume called the nucleus. 

At the distance of head on approach, the entire kinetic energy of α-particle is converted into electrostatic potential energy. This distance of head on approach gives an upper limit of the size of nucleus (denoted by r0 ) and is given by