Wave properties, of light

Describe the wave properties of light and how wavelength, frequency, and speed are related... 

The phenomena of interference and diffraction of light cannot be understood without introducing the wave concept. In fact, the wave properties of light were established precisely from these phenomena. Here, we will introduce the essential aspects of a propagating wave and the formulae needed to explain the optical effects described throughout this section. Let us first recall the one dimensional wave formula that we met for the first time during the physics classes in senior high school. 

Light behaves as both a wave and a particle. This duality has resulted in the division of optics into physical optics, which describes the wave properties of light geometric optics, which uses rays to model light behavior and quantum optics, which deals with the particle properties of light. Optics uses these theories to describe the behavior of light in the form of refraction, reflection, interference, polarization, and diffraction. 

However, these experiments demonstrate that light exhibits wave-particle duality. Some experiments reveal the wave properties of light, but others demonstrate its particle behaviour. Only light (photons), electrons and some atoms with a very small mass will show their wave nature in experiments. 

Altliough a complete treatment of optical phenomena generally requires a full quantum mechanical description of tire light field, many of tire devices of interest tliroughout optoelectronics can be described using tire wave properties of tire optical field. Several excellent treatments on tire quantum mechanical tlieory of tire electromagnetic field are listed in [9]. 

A hundred years ago it was generally supposed that all the properties of light could be explained in terms of its wave nature. A series of investigations carried out between 1900 and 1910 by Max Planck (1858-1947) (blackbody radiation) and Albert Einstein (1879-1955) (photoelectric effect) discredited that notion. Today we consider light to be generated as a stream of particles called photons, whose energy E is given by the equation... 

Here, the orbital phase theory sheds new light on the regioselectivities of reactions [29]. This suggests how widely or deeply important the role of the wave property of electrons in molecules is in chemistry. 

Heinrich Hertz in 1887 who used an oscillating circuit of small dimensions to produce electromagnetic waves which had all of the properties of light waves... 

But light is also a particle. Some properties of light cannot be explained by the wave-like nature of light, such as the photoelectric effect and blackbody radiation (see Section 9.4), so we also need to think of light comprising particles, i.e. photons. Each photon has a direction as it travels. A photon moves in a straight line, just like a tennis ball would in the absence of gravity, until it interacts in some way (either it reflects or is absorbed). 

From Snell s Law, sin(0j) m = sin(0j) nr. We have TIR when sin(Oj) > nr/rii, while we will have refraction and reflection when sin(0j) < nr/ni. In practical cases properties of light, such as phase, polarization and intensity, can be modulated inside the wave guide by a given measurand, which is interacting, for instance, with a CIM lying within the penetration depth for the evanescent field of the light localized near the external guide surface. 

A practical application of the wave properties of fast-moving electrons is the electron microscope, which focuses not visible-light waves but rather electron waves. Because electron waves are much shorter than visible-light waves, electron microscopes are able to show far greater detail than optical microscopes, as Figure 5.15 shows. 

Einstein started this great development as early as 1905 by an almost unimaginable act of vision, when he concluded that the concept of such an electromagnetic wave does not suffice to explain important properties of light. He drew the revolutionary conclusion that there must exist light-particles, the photons, The particle-wave duality was born, Einstein recognized die fertility of his idea, but lie was never completely satisfied with the conceptual basis of quantum mechanics, The lack of complete causality and the frequent use of probability instead of certainty were always a matter of deep concern for him. 

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,... 

Controversies still persist in the interpretation of the quantum theory of light and indeed more generally in quantum mechanics itself. This happens notwithstanding the widely held view that all the difficult problems concerning the correct interpretation of quantum mechanics were resolved a long time ago in the famous encounters between Einstein and Bohr. Recent books have been devoted to foundational issues [26] in quantum mechanics, and some seriously question Bohrian orthodoxy [27,28]. There is at least one experiment described in the literature [29] that purports to do what Bohr prohibits demonstrate the simultaneous existence of wave and particle-like properties of light. 

Light also has a particle nature—it can best be described as a stream of particles called photons. The properties of light emitted by glowing (red hot) objects and the photoelectric effect can be explained only with Ught as a stream of particles. The energy of the photons ( ) is related to the frequency of the waves (represented by v, Greek nu) ... 

The properties of light cannot be described completely by analogy with either ordinary waves or ordinary particles. In the discussion of some phenomena the description of light as vave motion is found to be the more useful, and in the discussion of other phenomena the description of light in terms of photons is to be preferred. 

Laser micro/nano drilling and on-site nanoscale measurement utilizing a coherence property of light and the dynamic control on wave-front... 

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