Physics 101
UNIT
1
Modern Physics
1.1
CLASSICAL PHYSICS
Newtons laws of motion are the basis of the most elementary principles of classical physics.
Equations based on these laws are the simplest and they are suitable for solution of simple dynamical problems, such as the motion of macroscopic bodies, Lagranges equations, Hamiltons equations and Hamiltons principle are also fundamental principles of classical mechanics, because they are consistent with each other and with Newtons laws of motion. Lagranges and Hamiltons equations are useful for solving many complicated dynamical problems. In principle, the properties of bulk matter must be deducible from the properties of electrons and atomic nuclei of which it is composed. However, it is found that many the observed properties of matter cannot be explained on the assumption that the particles obey the laws of classical mechanics.
At the end of 19th century and in the beginning of 20th century, many new phenomena such as photoelectric effect, x-rays, line spectra, nuclear radiation were discovered which wanted explanation on the basis of classical physics. Laws of classical mechanics failed to explain the above said newly observed properties of matter.
Therefore the need of new concepts was felt in many areas of physical sciences. The concepts developed led to a new mechanics called quantum mechanics. Another form of quantum mechanics is called wave mechanics. The mathematical theory of this mechanics was developed by Erwin
Schroedinger in 1926. Numerous problems of atomic physics have been solved by the application of quantum mechanics. To understand the development of wave mechanics, we begin with brief account of black body radiation, which could not be explained by classical mechanics. This is followed by description of some phenomena like the photoelectric effect, the Compton effect, etc.
Explanations of these phenomena are based on Plancks quantum hypothesis.
1.1.1
Black Body
1
Modern Physics
1.1
CLASSICAL PHYSICS
Newtons laws of motion are the basis of the most elementary principles of classical physics.
Equations based on these laws are the simplest and they are suitable for solution of simple dynamical problems, such as the motion of macroscopic bodies, Lagranges equations, Hamiltons equations and Hamiltons principle are also fundamental principles of classical mechanics, because they are consistent with each other and with Newtons laws of motion. Lagranges and Hamiltons equations are useful for solving many complicated dynamical problems. In principle, the properties of bulk matter must be deducible from the properties of electrons and atomic nuclei of which it is composed. However, it is found that many the observed properties of matter cannot be explained on the assumption that the particles obey the laws of classical mechanics.
At the end of 19th century and in the beginning of 20th century, many new phenomena such as photoelectric effect, x-rays, line spectra, nuclear radiation were discovered which wanted explanation on the basis of classical physics. Laws of classical mechanics failed to explain the above said newly observed properties of matter.
Therefore the need of new concepts was felt in many areas of physical sciences. The concepts developed led to a new mechanics called quantum mechanics. Another form of quantum mechanics is called wave mechanics. The mathematical theory of this mechanics was developed by Erwin
Schroedinger in 1926. Numerous problems of atomic physics have been solved by the application of quantum mechanics. To understand the development of wave mechanics, we begin with brief account of black body radiation, which could not be explained by classical mechanics. This is followed by description of some phenomena like the photoelectric effect, the Compton effect, etc.
Explanations of these phenomena are based on Plancks quantum hypothesis.
1.1.1
Black Body