ATOMIC AND NUCLEAR PHYSICS In this unit, the students are exposed to • electric discharge through the gases • determination of specific charge of by an electron J.J. Thomson experiment • determination of electronic charge by Millikan’s oil drop experiment • atom models – J.J. Thomson and Rutherford • Bohr atom model and hydrogen atom • atomic spectrum and hydrogen spectrum • structure and properties of nucleus • various classification of nuclei based on atomic number and mass number • mass defect and binding energy • relation between stability and binding energy curve • alpha decay, beta decay and gamma emission • law of radioactive decay • nuclear fission and fusion • elementary ideas of nuclear reactors • qualitative idea of elementary particles All of physics is either impossible or trivial. It is impossible until you understand it, and then it becomes trivial – Ernest Rutherford Learning Objectives INTRODUCTION Atom Apple Apple Apple Earth Earth Atom Atom Same size Same size Figure .
Comparision of size of an atom with that of an apple and comparision of size of an apple with that of the Earth . In earlier classes, we have studied that anything which occupies space is called matter. Matter can be classified into solids, liquids and gases. In our daily life, we use water for drinking, petrol for vehicles, we inhale oxygen, stainless steel vessels for cooking, etc.
Experiences tell us that behaviour of one material is not the same as that of another, which means that the physical and chemical properties are different for different materials. In order to understand this, we need to know the fundamental constituents of materials. - - - - Unit Atomic and Nuclear physics But by special arrangement, one can make a gas to conduct electricity. A simple and convenient device used to study the conduction of electricity through gases is known as gas discharge tube.
The arrangement of discharge tube is shown in Figure . . It consists of a long closed glass tube (of length nearly cm and diameter of cm) inside of which a gas in pure form is filled usually. The small opening in the tube is connected to a high vacuum pump and a low-pressure gauge.
This tube is fitted with two metallic plates known as electrodes which are connected to secondary of an induction coil. The electrode connected to positive of secondary is known as anode and the electrode to the negative of the secondary is cathode. The potential of secondary is maintained at about kV. High potential difference Gas