Nuclear Physics

** Atom and Introduction to Nuclear physics **

Introduction

Alpha-particle scattering

2.1 Experimental set-up

➢ Alpha particle o is a high-energy helium nucleus with 2 protons and 2 neutrons. o has 2 positive charges. ➢ Gold foil was chosen since it has a high atomic mass. Thin gold foil, ~10-6m was bombarded by high-energy alpha particles. ➢ Angular deflections/ scattering of alpha particles were measured by observing the scintillation when alpha particles struck on the zinc sulphide screen on the turntable microscope. No. of bright spots vs. angles was measured. ➢ The experiment was carried out in an evacuated container to avoid collision between alpha particles and air molecules.

Fig 1 : Expérimental set up

Fig 2 : Trajectory of (-particles around a nucleus
2.2 Observations & conclusions

|Observations |Explanation |
|Most of the alpha particles, ~90%, passed through the foil | |
|undeflected. | |
| | |
| | |
| | |
|A small number of particles, 1 in 800 particles, were | |
|scattered considerably at large angles, deflected by