Atomic World

Unit Overview

The nature of the smallest particles making up all matter has been a topic of vigorous debate among scientists, from ancient times through the exciting years in the first few decades of the 20th century to the present. Classical physics deals mainly with particles and waves, as two distinct entities. Substances are made of very tiny particles. Waves, such as those encountered in visible light, sound and heat radiations, behave very differently from particles. At the end of the 19th century, particles and waves were thought to be very different and could not be associated with each other. When scientists looked more closely at the nature of substances, contradictory phenomena that confused scientists began to appear. Classical concepts in Mechanics and Electromagnetism cannot explain the phenomena observed in atoms, or even the very existence of atoms. Studies on the structure of an atom and the nature of light and electrons revealed that light, the wave nature of which is well known, shows particle properties, and electrons, the particle nature of which is well known, show wave properties. In this elective topic, students learn about the development of the atomic model, the Bohr’s atomic model of hydrogen, energy levels of atoms, the characteristics of line spectra, the photo-electric effect, the particle behaviour of light and the wave nature of electrons, i.e. the wave-particle duality. Through the learning of these physical concepts and phenomena, students are introduced to the quantum view of our microscopic world and become aware of the difference between classical and modern views of our physical world. Students are also expected to appreciate the evidence-based, developmental and falsifiable nature of science. Advances in modern physics have led to many applications and rapid development in materials science in recent years. This elective includes a brief introduction to nanotechnology, with a discussion on the advantages and use of transmission electron microscopes (TEM) and scanning tunnelling microscopes (STM), as well as some potential applications of nano structures. Nanotechnologies have been around for hundreds of years, although the underlying physics was not known until the 20th century. For example, nano-sized particles of gold and silver have been used as coloured pigments in stained glass since the 10th century. With better understanding of the basic principles, more applications have been found in recent years. These applications include the potential use of nano wires and nano tubes as building materials and as key components in electronics and display. Nano particles are used in suntan lotions and cosmetics, to absorb and reflect ultra-violet rays. Tiny particles of titanium dioxide, for example, can be layered onto glass to make self-cleaning windows. As in any newly developed area, very little is known, for example, about the potential effects of free nano particles and nano tubes on the environment. They may cause hazards to our health and might lead to health concerns. Students are, therefore, expected to be aware of the potential hazards, and issues of risk and safety to our life and society in using nanotechnologies. In studying this elective topic, students are expected to have basic knowledge about force, motion, and waves. Some basic concepts of covalent bonds of electrons would be helpful in understanding the structures and special properties of nano materials. Knowledge of electromagnetic forces, electromagnetic induction and electromagnetic spectrum is also required.