Corpuscular Properties of Light

A derived quantity is the wave number v, which is the reciprocal of X and specifies the number of wavelengths per unit distance (cm-1). The energy contained in light is quantized. A quantum of energy A Ex is one photon. Mathematically, this is defined as 

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Quantum theory started as an explanation of electromagnetic effects (black-body radiation) in terms of corpuscular properties of light, expressed... 

The concept of dual character of light is particularly relevant to the discussion of optical sensors. In this introductory section, the basic quantized (corpuscular) aspects of light as they relate to optical sensors are reviewed first, followed by a brief review of physics of optical waveguides and optical fibers which rely on wavelike (continuous) properties of light. Detailed information can be found in analytical (e.g., Skoog et al., 1998) and specialized textbooks (e.g., Hollas, 2004). 

Experiments by MilUken in 1908 soon confirmed Einstein s predictions. In 1921, A.H. Compton succeeded in determining the motion of a photon and an electron both before and after a collision between them. He found that both behaved like material bodies in that both kinetic energy and momentum were conserved in the collision. The photoelectric effect and the Compton effect, then, seemed to demand a return to the corpuscular theory of light. The reconciliation of these apparently contradictory experiments has been accomplished only since about 1930 with the development of quantum electrodynamics, a comprehensive theory that Includes both wave and particle properties of photons. Thus, the theory of light propagation is best described by an electromeignetic wave theory while the Interaction of a photon with matter is better described as a corpuscular phenomenon. 

The development of wave mechanics has been made possible through the introduction by de Broglie of a new principle dealing with the wave character of matter. The basis of this principle is the recognition that different interpretations are appropriate to different kinds of measurements thus atoms and electrons which have hitherto been regarded as discrete particles arc considered to possess a dual character, in the sense that they may possess both corpuscular and wave properties. A duality of a similar kind had been revealed earlier in studies on the propagation of light. 

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. 

The popular image of total internal reflection is based on the corpuscular model of radiation. The alternative wave model explains different properties. A result of this model is the theory of light propagation by clearly distinguished... 

The Erench physicist Louis de Broglie proposed in 1924 that not only light but all matter has a dual nature and possesses both wave and corpuscular properties. He reasoned that there should be symmetry in nature If a radiant corpuscle—-that is, a photon—has a frequency and a wavelength and therefore has wave properties, why should not a material particle also have wave properties (p. 429, original italics). .. When de Broglie first published his wave theory of matter, there was no experimental evidence to support his bold hypothesis. Within three years, however, two different experiments had been performed that demonstrated the diffraction of a beam of electrons. Clinton J. Davisson, assisted by L. H. Germer,. .. observed the diffraction of electrons when a beam of electrons was directed at a nickel crystal (Segal 1989, p. 431, underlined added). 

In the late nineteenth century, a whole set of experiments progressively lead to the conclusion that classical physics, namely, Newtonian mechanics, thermodynamics, and nascent electromagnetism, were unable to explain empirical evidence gathered by experimentalists. Scientists of that time were unable to conciliate two apparent contradictory aspects exhibited by radiation and matter. Some experiments demonstrated that light behaved like a wave, while others showed a rather corpuscular nature. On the other hand, electrons, protons, and the other massive particles would manifest wave-like properties in certain experimental conditions. 

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