Rutherford's Alpha Particles Scattered with Scattering Angle

 Rutherford's Alpha Particles Scattered with Scattering Angle.

In 1911, Geiger and Marsden did the experiment based on the Rutherford's scattering alpha particles by gold foil.

A source of Alpha particles are kept inside a thick lead box with with a hole. The alpha particles coming through the hole made of lead box pass through another hole made on the lead screen. These particles are now allowed to fall on a thin gold foil and it is observed that the alpha particles passing through gold foil are scattered through different angles. A movable screen (from 0° to 180°) which is made up of zinc sulphide (ZnS) is kept on the other side of the gold foil to collect the scattered alpha particles. Whenever alpha particles strike the screen, a flash of light is observed which can be seen through a microscope. 

Rutherford's Alpha Particles Scattered with Scattering Angle 

Rutherford proposed an atom model based on the results of the alpha scattering experiment. In this experiment alpha particles were allowed to fall on the atoms of a metallic gold foil.

(a) Most of the alpha particles were un-deflected through the gold foil and went straight.

(b) Some of the alpha particles were deflected through a small angle.

(c) A few alpha particles (one in thousand) were deflected through the angle more than 90°.

(d) Very few alpha particles returned back (back scattered) - that is, deflected back by 180°.

" An alleged scientific discovery has no merit unless it can be explained to a barmaid. " 

                                          ---Ernest Rutherford---