Nature of Light Series on Light Scattering - by KRS Murthy

Nature of Light Series on Light Scattering

KRS Murthy

Let us investigate the nature of light in scattering. In scattering the light is scattered when it hits or impinges on to matter. The light is scattered.

Scattering is a general category, of which there are special cases of scattering. One example is reflection, which has a geometrical follow on relation between incident light and the reflected light. Reflection happens when the surface of the matter on which light is incident is smooth, whether it be a plane like in a mirror, or a curved mirror to include concave and convex mirrors as examples and even includes a variety of curve shapes of mirrors.

Particularly, the term “scattering” is used in which light in the form of propagating energy is scattered. In scattering the incident rays of light is deflected from its straight path. One example is in which the ray of light is deflected by irregularities in the propagation medium, or particles, or in the interface between two media. Deviations from the particular case of reflection due to irregularities on a surface are also usually considered to be a form of scattering. When these irregularities are considered to be random and dense enough that their individual effects average out, this kind of scattered reflection is commonly referred to as diffused reflection.

Scattering or absorption of light either in part or all of the wavelengths of the light spectrum happens when light is incident on an opaque object. When light is incident on a transparent object, part or most of the incident light passes through the transparent medium.

It is important to specially note that 100% of the incident light never passes through even the best transparent object or medium. No medium in nature is 100% transparent. Even when the light passes through in the air, or the light that comes from the sun to the earth part of it is scattered by the air particles or dust particles, even though very small. We see the objects near and far only because they absorb part of the incident light and scatter the remaining. Even out of the scattered light, only a small part is collected by our eye. It is the brain, its memory, it’s amazing processing power, and most importantly ability to almost unknown in our daily life construct or reconstruct the image we see through our eyes. Scattering of light, including the special case of reflection is vital to our survival, and also of most of the animals. The only exceptions are insects, bats and few other in the animal kingdom wave, which do not have the eyes, but use other senses like smell, sound, ultrasound and vibrations.

Most objects that one sees are visible due to light scattering from their surfaces. Indeed, this is our primary mechanism of physical observation. Light scattering depends on the wavelength or frequency of the incident light. For example, when an object appears to be yellow in color to the human eye, out of the full range of wavelengths (or frequencies) of the incident light, only the wavelength corresponding to yellow is reflected, with remaining part of the incident light spectrum is absorbed.

Since visible light has wavelengths on the order of hundreds of nanometers objects much smaller than this cannot be seen, even with the aid of a microscope. Colloidal particles as small as 1 µm have been observed directly in aqueous suspension.

Mechanisms of diffuse reflection include surface scattering from roughness andsubsurface scattering from internal irregularities such as grain boundaries inpolycrystalline solids.

Photos, Diagrams and Cartoons are credited to Wikipedia

 Light scattering could happen by the incident rays of light interacting with molecules, or atoms. Scattering at the atomic level happens by the interaction of the incident light with the electrons in the atom. 

Murthy’s Interpretation on Different Types of Scattering

All interactions in nature are field interactions.  Charged particles in nature, due to their very nature of charge, have an electric field around them. As they move in space the field around the charged particle changes. The change in the electric field results in magnetic field, as the magnetic field is a symbiotic and conjoined twin of the changing electric field, except that the electric field and the magnetic field change in orthogonal relationship with each other. When the electric charge moves along a path or locus, the electric charge field increases from zero from its front, which is the direction of its movement, to a peak and reduce to zero at its tail point. Being orthogonal to the electric field, the magnetic field is zero when and at the point of the peak of the electric field, and goes to a peak when and at the same point when the electric field has gone from peak to zero. It is a push – pull relationship between the electric and magnetic fields.

This relationship explanation is true not only to the moving electric charge, and also to the light transmission. However, the charges particle may move much slower than the speed of light. If and when a charged particle moved faster and faster approaching the speed of light and ultimately reach the limit, it would have transformed into light.

The electron in an atom, orbiting around the nucleus, can gain a quantum of energy as it interacts with a ray of light incident on it. This quantum of energy results in an increased momentum in the electron. With this increased quantum of energy, in its resulting increased momentum pushes it to the higher orbit or a higher state of energy. It is important to understand that the interaction between the electromagnetic form of light and the electron is a field interaction or multiple fiend interactions, all reducible to individual field interaction between fundamental or elementary particles; one specific case being light - electron field interaction.. In this particular case, the field interaction happens at the intra-atomic scale or inside the atom. The light and the electron “do not touch each other”.

The different forms of scattering are only a result of this basic and fundamental field interaction. The different scattering and effects of light matter interactions are all effects of the light – electron interaction. Based on what the electron is doing in an atom, molecule, in solid, liquid, gas and their combinations in the matter the light - electron field interactions vary, and especially the quantum of energy donated by the light to the electron vary. For example, in a molecule made up of multiple atoms, the energy bond between the atoms is created by a shared electron between them. The shared electron has field relationship with the multiple atoms’ nucleus and the other non-shared electrons. The field relationship of the shared electron in its extended combined multiple atom family results in this energy bond. The quantum of energy required to alter this bond relationship status quo depends on the different atomic and molecular configuration in the matter, be it a solid, liquid or gas; be it a multi-phase like a colloidal mixture; be it a chain of molecules like a polymeric chain; be it a crystal; be it a metal; be it a nanowire or nano dot. It also depends on the temperature and pressure. The various semicolon separated I have given in the preceding sentence are only few of many possibilities. When the appropriate quantum of energy is donated by the incident light to the electron in this example, not only the electron receives this specific quantum of energy, the increased energy may have effect not only on the electron, but also its extended family relationship with other electrons, nuclei, the different atoms in the molecule, and also other molecules in the multiple molecules chain bigger family; the response and the result of the original light – electron field interaction is not only by the electron, but the whole extended family or even the bigger family of multiple entangled molecules. Not only the electron is entangled with in its atom host, it is entangled with other atoms sharing this electron, and the extended entanglement with the molecule or bigger family of multiple molecules.

Depending on the actual details of the primary, secondary and tertiary entanglement, different effects were discovered by various scientists in the last two to three centuries. The list of effects is very long. Therefore, I am listing only few here in this document, but will extend this list in the next few days.

Importance of KRS Murthy’s Contribution

While many discoveries have been made for the interaction of light with matter in different forms, and respective discoveries interpreted by various other scientists, further test variations and resulting corollary discoveries presented, none of the scientists have provided a unified approach to the large list of discoveries, from the basics of field interactions and the basic and fundamental interactions between the electron and incident electromagnetic radiation, like light, and the full spectrum of electromagnetic radiation.

My interpretation is that in all of nature all scattering and related effects, in all forms of matter, including the multi-phase, arise from the basic and fundamental nature of field interactions between the fundamental and elementary particles in the nature.

1. Rayleigh Scattering
2. Raman Scattering
3. Mei Scattering
4. Tyndall Scattering
5. Brillouin Scattering
6. Dynamic and Static Scattering
7. Elastic and Inelastic Scattering

The Bicycle Analogy

Caution about Analogy of a concept to the Main Concept

Before I give an analogy, let me emphasize that analogies are meant only to drive home a point. The analogical relationship should not be over extended in any sense. Analogy relationship to the main concept or subject of discuss is NOT elastic.

Just to give an analogy, think of a bicycle. When one of the peddle goes up the opposite peddle goes down, and vice versa. The feet peddling also follow this relationship. The electric and magnetic fields have similar relationship. As both peddles continue in this temporally orthogonal relationship, the bicycle move forward or back word. Analogically, the light transmission with temporally orthogonal relationship between the electric and magnetic fields behave, and the light pulsations, together a ray of light, move in the direction of the ray of light.