Question

(a) Explain briefly how Rutherford scattering of -particle by a target nucleus can provide information on the size of the nucleus.
(b) Show that density of nucleus is independent of its mass number A.

Answer 1

(a)Rutherford scattering experiment helps to determine the size of the nucleus.

Rutherford directed beams of alpha particles (which are the nuclei of helium atoms and hence positively charged) at thin gold foil to test this model and noted how the alpha particles scattered from the foil.

Rutherford concluded that since alpha particles are positively charged, for them to be deflected back, they needed a large repelling force. ... According to Kinetic theory, the size of an atom is around 10-10 m or around 10,000 to 100,000 times the size of the nucleus proposed by Rutherford.

(b)Nuclear density is independent of the mass number.

Let the volume of nucleus beV, mass of the nucleus M,mass of nucleon be m, A be the no. Of nucleons

Hence total nuclear massM=mA

V is proportional to r^3, where r is radiys of the nucleus.

r is proportional  to cube root of A.

So V is proportional to

Thusnuclear density is independent of mass number A.

Answer 2

Rutherford Scattering Experiment

Explanation:

• Rutherford describe the atom structure, he considered the atom made of nucleus and revolving electrons

• Nucleus are considered small and dense by performing experiment of scattering of light by nucleus.

• He proposed that most of the alpha particle go straight atom contain large empty space.

• Few alpha particle come back , which make him realized that nucleus are present in the centre of atom in concentrated form.

• Nucleus density is ratio of its mass and volume. when we compare it with mass no. of atom we realized that density-independent of its mass no.