On the nature of light

In another set of experiments, he took the beam emerging from a prism— separated into colors—and let it pass through a second prism, inverted with respect to the first. In this arrangement, the second prism performed the opposite function of the first. The result he obtained was a combination of the separated 

University of Chicago Press, Chicago (1987). Sir Isaac Newton, Optics, pp. 20, 26, Dover Publications, New York (1979). 

Interference is the phenomenon that distinguishes waves from matter. While waves can interfere with one another in a constructive (when the superposition of the waves add up) or destructive (when the superposition of the waves cancel each other) manner, matter cannot. It was thus reasonable for many scientists of the seventeenth and eighteenth centuries to describe light either in terms of moving particles or of waves.  

The corpuscular theory of light, expounded by Sir Isaac Newton, states that light is made up of very small corpuscles or streams of particles that are emitted from 

University of Chicago Press, Chicago (1987). 

---

Young, T. Lecture XXXIX. On the nature of light and colours. A Course of Lectures on Natural Philosophy and the Mechanical Arts. pp. 457-471 (1807). 

Part V covers spectroscopic methods of analysis. Basic material on the nature of light and its interaction with matter is presented in Chapter 24. Spectroscopic instruments and their components are described in Chapter 25. The various applications of molecular absorption spectrometric methods are covered in some detail in Chapter 26, while Chapter 27 is concerned with molecular fluorescence spectroscopy. Chapter 28 discusses various atomic spectrometric methods, including atomic mass spectrometry, plasma emission spectrometry, and atomic absorption spectroscopy. 

There is no question that the three reports, the photoelectric effect, the special relativity and the Brownian motion published by Einstein in 1905 changed the traditional consciousness of researchers in the 20th century. The report on the photoelectric effect clarified an old problem in the wave theory of light by linking discussions on the nature of light and the quantum hypothesis originating in Planck s study of specific heat. The report on special relativity refuted the ether theory and created an entirely new field. The report on Brownian motion, aimed at the very existence of atoms and molecules, created the theory... 

The discussion of the electronic structure of an atom is so closely interwoven with an understanding of the nature of light that we shall include here a brief review on the nature of light,... 

Spectral lines are fiirther broadened by collisions. To a first approximation, collisions can be drought of as just reducing the lifetime of the excited state. For example, collisions of molecules will connnonly change the rotational state. That will reduce the lifetime of a given state. Even if die state is not changed, the collision will cause a phase shift in the light wave being absorbed or emitted and that will have a similar effect. The line shapes of collisionally broadened lines are similar to the natural line shape of equation (B1.1.20) with a lifetime related to the mean time between collisions. The details will depend on the nature of the intemrolecular forces. We will not pursue the subject fiirther here. 

Figure Bl.9.1. Diagrams showing that x-ray and light scattering involve extra-nuclear electrons, while neutron scattering depends on the nature of the atomic nucleus.

This also illustrates the use of different wavelengths of light to obtain much more infomration on the nature of the film. Here A and T are plotted versus the wavelength of light ( ) and the line drawn tln-ough these data represents a fit calculated for the various fihns of yttrium oxide deposited on silica as shown at tire bottom of the figure [40],... 

In Chapter IV, Englman and Yahalom summarize studies of the last 15 years related to the Yang-Mills (YM) field that represents the interaction between a set of nuclear states in a molecular system as have been discussed in a series of articles and reviews by theoretical chemists and particle physicists. They then take as their starting point the theorem that when the electronic set is complete so that the Yang-Mills field intensity tensor vanishes and the field is a pure gauge, and extend it to obtain some new results. These studies throw light on the nature of the Yang-Mills fields in the molecular and other contexts, and on the interplay between diabatic and adiabatic representations. 

A number of studies have compared normal mode analysis predictions with results from more realistic simulation techniques or experiments. These studies shed light on the nature of the conformational energy surface and the effect of solvent. 

Studies in the photoinitiation of polymerization by transition metal chelates probably stem from the original observations of Bamford and Ferrar [33]. These workers have shown that Mn(III) tris-(acety]acetonate) (Mn(a-cac)3) and Mn (III) tris-(l,l,l-trifluoroacetyl acetonate) (Mn(facac)3) can photosensitize the free radical polymerization of MMA and styrene (in bulk and in solution) when irradiated with light of A = 365 at 25°C and also abstract hydrogen atom from hydrocarbon solvents in the absence of monomer. The initiation of polymerization is not dependant on the nature of the monomer and the rate of photodecomposition of Mn(acac)3 exceeds the rate of initiation and the initiation species is the acac radical. The mechanism shown in Scheme (14) is proposed according to the kinetics and spectral observations ... 

An alternative stream came from the valence bond (VB) theory. Ovchinnikov judged the ground-state spin for the alternant diradicals by half the difference between the number of starred and unstarred ir-sites, i.e., S = (n -n)l2 [72]. It is the simplest way to predict the spin preference of ground states just on the basis of the molecular graph theory, and in many cases its results are parallel to those obtained from the NBMO analysis and from the sophisticated MO or DFT (density functional theory) calculations. However, this simple VB rule cannot be applied to the non-alternate diradicals. The exact solutions of semi-empirical VB, Hubbard, and PPP models shed light on the nature of spin correlation [37, 73-77]. 

Solvent effects on the rate of the decarbonylation of MeCOMn(CO)5 were examined by Calderazzo and Cotton (50) and are presented in part in Table IV. In general they are very small, and no regular trends can be discerned. This virtual lack of dependence of the rate on the nature of the solvent and very little correlation between the rate and the dielectric constant of the solvent are typical of substitution reactions of metal carbonyls (J). In the light of the foregoing, a qualitative observation that CpFe(CO)2-COMe decarbonylates much more readily on treatment at reflux in nonpolar heptane or cyclohexane than in polar dioxane is somewhat intriguing 219). 

---