Introduction to physics
Physics deals with matter and energy and the relation between them. The word Physics is derived from the Greek word Physis which means nature. It is a science which deals broadly with nature and changes in nature. It is perhaps the most comprehensive science, since it examines the behavior of all kinds of matter from the smallest particles to gigantic galaxies. It deals with distances, time scales and temperatures of a very wide range.
A study of nuclear phenomena involves distances of the order of 1OE5m, masses of the order of 10-31 kg and processes that may last only for about 10-15 s, while a study of astronomical phenomena involves distances of the order of
billions of light years (light year is roughly 9.5 x: 1012 km, being the distance travelled by light in one year), masses of the order of 1026 kg and time intervals of the order of billions of years. Some cryogenic phenomena occur at temperatures of about 2700 C and the temperatures of
some stars are estimated to be of the order of millions of degrees centigrade.
These ranges include processes that Occur in our day to day life where distances involved range from mm to km, masses range from mg to kg and time intervals range from seconds to centuries and temperatures from 50 C to 15000 C.
Physics Laws and Theories
It is observed that the behavior of many physical systems can be explained on the basis of a small number of fundamental laws. These laws are conveniently expressed in the language of mathematics. Based on the laws, physical theories that will predict and/or explain the results of some experiments are enunciated.
The laws and theories are modified whenever there is a discrepancy between predictions and observations, or where new generalized explanations of observed phenomena are required. For example, a study of the formation of shadows led Sir Isaac Newton to believe that light was made up of corpuscles or particles. The diffraction of light at a straight edge could be understood assuming that light was propagated in the form of waves. Both these could not account for the photo electric effect. This led to the development of the quantum theory of light.