A Rutherford’s experiment on the scattering of ∝ particles (Geiger mariden Experiment):

A radioactive source of ∝ - particle like Bismuth Bi is enclosed in thick block, provided with narrow the ∝-particle from this source are collimated into a narrow beam through a slit. The beam is allowed to fall on a thin gold foil of thickness 2.1 x 10^-7 m. The alpha particle scattered in different direction which consists  of a zinc sulphate screen and a microscope.

Observations:

A graph is drawn between the scattering angle and the number N(θ) of the ∝-particle scattered at an angle θ very large number of ∝-particles.

The graph in fig.(b) reveals the following fact:

1. Most of the ∝-particle pass straight through the gold foil and suffers in small deflections.
2. A few ∝- particles about 1 in 8000 get deflected through 90° or more.
3. Occasionally an ∝ particle gets rebounded from the gold foil suffering a deflection of nearly 180°.

Significance of result:

Rutherford concluded the following important facts about an atom:

1. As most of ∝- particles pass straight through the foil so most of the space within the atom must be empty.
2. To explain large angle scattering of alpha particles Rutherford suggested that all the positive charge and the mass of the atom is concentrated in a very small region called Nucleus of the atom.

3.The nucleus surrounded by a cloud of electrons whose total negative charge is equal to the total +ve charge on the nucleus so that the atom as whole is electrically neutral.