Wave properties of electromagnetic radiation

Thus, for electromagnetic radiation of frequency, V, the wavelength in vacuum is longer than in other media. Another unit used to describe the wave properties of electromagnetic radiation is the wavenumber, V, which is the reciprocal of wavelength... 

A significant change in the theoretical treatment of atomic structure occurred in 1924 when Louis de Broglie proposed that an electron and other atomic particles simultaneously possess both wave and particle characteristics and that an atomic particle, such as an electron, has a wavelength X = h/p = h/mv. Shortly thereafter, C.J, Davisson and L.H. Germer showed experimentally the validity of this postulate. Dc Broglie s assumption that wave characteristics are inherent in every atomic particle was quickly followed by the development of quantum mechanics, in its most simple form, quantum mechanics introduces the physical laws associated with the wave properties of electromagnetic radiation into the physical description of a system of atomic particles. By means of quantum mechanics a much more satisfactory explanation of atomic structure can be developed. 

The wave properties of electromagnetic radiation are described by two interdependent variables, as Figure 7.1 shows ... 

Walls, accumulation, 884-887 Wave properties of electromagnetic radiation, 133, 135,137, 139, 141, 143... 

A full explanation of the properties of light requires both the wave theory of electromagnetic radiation and the quantum theory. Most photochemical processes are best understood in terms of the quantum theory, which says that light is made up of discrete particles called quanta or photons. Each quantum carries an amount of energy, S, determined by the wavelength of the light, A. Equation 13.1, in which h is Planck s constant and c is the speed of light in a vacuum,... 

Infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy (Chapter 14) both use a form of electromagnetic radiation as their energy source. To understand IR and NMR, therefore, you need to understand some of the properties of electromagnetic radiation— radiant energy having dual properties of both waves and particles. 

Many of the properties of electromagnetic radiation are conveniently described by means of a classical sinusoidal wave model, which embodies such characteristics as wavelength, frequency, velocity, and amplitude, in contrast to other wave phenomena, such as sound, electromagnetic radiation requires no supporting medium for its transmission and thus passes readily through a vacuum. 

A few years after de Broglie pubUshed his theory, the wave properties of the electron were demonstrated experimentally. When X-rays pass through a crystal, an interference pattern results that is characteristic of the wavelike properties of electromagnetic radiation. This phenomenon is called X-ray diffraction. As electrons pass through a crystal, they are similarly diffracted. Thus, a stream of moving electrons exhibits the same kinds of wave behavior as X-rays and all other types of electromagnetic radiation. 

The major part of this book will be concerned with the wave properties of matter, but it will be helpful, at the outset, to spend a little time looking at the particle properties of electromagnetic radiation because similar concepts apply in both cases. 

The wave theory of electromagnetic radiation can explain a number of observed phenomena associated with light, such as diffraction, refraction, and interference, but fails to explain other properties. These include such things as the photoelectric effect and the emission and absorption of radiation by bodies. Instead, those phenomena involving interaction of light with matter are explained by utilizing the corpuscular character of electromagnetic radiation. 

We have evidence for the wavelike nature of light. We also know that a beam of light photons behaves like a stream of tiny packets of energy called photons. So what is light exactly Is it a particle Is it a wave Scientists have agreed to explain the properties of electromagnetic radiation by using both wave and particle properties. Neither explanation is ideal, but currently these are our best models. 

Before we go any further, it is a useful exercise to remind ourselves of the fundamental properties of electromagnetic radiation. They are transverse waves, with perpendicular oscillating electronic and magnetic components, that travel at the speed of light, c, such that ... 

Two additional wave properties are power, P, and intensity, I, which give the flux of energy from a source of electromagnetic radiation. 

Light has a dual character - it may be described either as a wave motion or as a stream of moving particles. Since light is a form of electromagnetic radiation, its properties, as with all forms of electromagnetic radiation, are... 

The various forms of spectroscopy find widespread application in kinetic studies. They are usually well suited for application to in situ studies of the characteristics of the reaction mixture. The absorption by a reacting system of electromagnetic radiation (light, microwaves, radio-frequency waves, etc.) is a highly specific property... 

De Broglie s hypothesis of matter waves received experimental support in 1927. Researchers observed that streams of moving electrons produced diffraction patterns similar to those that are produced hy waves of electromagnetic radiation. Since diffraction involves the transmission of waves through a material, the observation seemed to support the idea that electrons had wave-like properties. 

In the study of chemistry, the properties and composition of matter are investigated, along with the nature of electromagnetic radiation and how it affects matter. Electromagnetic radiation is radiant energy that exhibits wave properties and travels at the speed of light (when in a vacuum). 

It turns out that electromagnetic waves exhibit properties of both waves and particles, or equally valid, electromagnetic waves are neither waves nor particles. This fundamental paradox is at the heart of quantum theory. You can perform experiments that unequivocally demonstrate light is definitely a wave. You can also perform experiments that unequivocally demonstrate light is definitely a particle. Nonetheless, there is one important relationship that allows the energy of electromagnetic radiation to be calculated if the frequency or wavelength is known ... 

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