Light, modern theory energy

The modern theory of the electronic structure of the atom is based on experimental observations of the interaction of electricity with matter, studies of electron beams (cathode rays), studies of radioactivity, studies of the distribution of the energy emitted by hot solids, and studies of the wavelengths of light emitted by incandescent gases. A complete discussion of the experimental evidence for the modern theory of atomic structure is beyond the scope of this book. In this chapter only the results of the theoretical treatment will be described, These results will have to be memorized as rules of the game, but they will be used so extensively throughout the general chemistry course that the notation used will soon become familiar. 

The theory of color and light production, however, involves the energy levels available for electrons in atoms and molecules, according to the beliefs of modern chemical theory. In an atom or molecule, there are a number of "orbitals" or energy levels that an electron may occupy. Each of these levels corresponds to a discrete energy value, and only these energies are possible. The energy is said to be quantized, or restricted to certain values that depend on the nature of the particular atom or molecule. 

The work of deBroglie and Heisenberg represents a departure from the Bohr theory and paved the way for the development of modern atomic theory. Although Bohr s concept of principal energy levels is still valid, restriction of electrons to fixed orbits is too rigorous in light of Heisenberg s principle. All current evidence shows that electrons do not, in fact, orbit the nucleus. We now speak of... 

These two engineering mathematicians became involved In theorising the early aeronautical structures. The large-scale experiments and easily appreciable failure modes of such light frames influenced Pippard and Baker in different ways, and the dialectic between theory and experiment, described above between countries, departments and individuals, was to be played out within the career of John Baker. As Pippard went on to embellish classical theory. Baker made a new departure, one based on observation and which joined old notions of geometry with modern energy methods. Plastic theory promised another revolution in structural design. 

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