Modern physics developed mainly because of the discovery that many physical phenomena could not be explained by classical physics. Major developments in mechanics continued in the 18th century, but the fields of thermodynamics and electricity and magnetism were not developed until the latter part of the 19th century, principally because before that time the apparatus for controlled experiments was either too crude or unavailable.ДЄ new era in physics, usually referred to as modern physics, began near the end of the 19th century. Important contributions to classical physics were provided by Newton, who developed classical mechanics as a systematic theory and was one of the originators of calculus as a mathematical tool. Classical physics, which means all of the physics developed before 1900, includes the theories, concepts, laws, and experiments in classical mechanics, thermodynamics, and electromagnetism. Hence, EinsteinвЂ™s is a more general theory of motion. In contrast, the special theory of relativity developed by Albert Einstein (1879вЂ“1955) in the early 1900s gives the same results as NewtonвЂ™s laws at low speeds but also correctly describes motion at speeds approaching the speed of light. For example, the laws of motion discovered by Isaac Newton (1642вЂ“1727) in the 17th century accurately describe the motion of bodies at normal speeds but do not apply to objects moving at speeds comparable with the speed of light. Many times a theory is satisfactory only under limited conditions a more general theory might be satisfactory without such limitations. When a discrepancy between theory and experiment arises, new theories must be formulated to remove the discrepancy. The fundamental laws used in developing theories are expressed in the language of mathematics, the tool that provides a bridge between theory and experiment. The main objective of physics is to find the limited number of fundamental laws that govern natural phenomena and to use them to develop theories that can predict the results of future experiments. Like all other sciences, physics is based on experimental observations and quantitative measurements.

Fundamentals of physics pdf