The Heavens Declare His Handiwork

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Thomas Lee Abshier, ND

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Polarized Light

By: Thomas Lee Abshier, ND

o Non-metallic substances reflect light polarized parallel to their surfaces more than light polarized vertically.  

§ This may be because the vertically oriented electric vector engages the bulk of the material more than the parallel E field vector.  In other words, a portion of the E field vector penetrates into the non-metallic substance and has the potential to engage a surface or point for reflection.  Whereas, a horizontally polarized photon is skimming the top of the surface along its entire breadth.

§ The reflectivity of metallic substances is dependent upon the angle of incidence, just non-metallic substances.  But, the reflectivity may be so much higher because of the large numbers of concentration of conduction band orbitals.

§ Metallic substances absorb photons for the same reason that non metals do, the photons penetrate, and are captured.  The evidence of photonic absorption is obvious to the person who has touched a quarter that has been sitting in the sun – it got hot.  There were photons that penetrated, transmitted their energy to electrons, electrons that collided with nuclei and shook the lattice, raising the heat of the metal.

o Reflection: Photons approach the reflective interface with two components of velocity, 1) perpendicular, and 2) parallel to the interface.  

§ The perpendicular component of the photon attempts to compresses the electron cloud into the nucleus, and the parallel component of the photon’s energy moves the electron cloud tangential to its orbit.  

§ The energy directed perpendicular to the interface will produce a rebound of energy that reverses the perpendicular component of the photon’s velocity.

§ The energy directed parallel to the interface will either not interact with the reflective substance, or simply conduct forward in the metallic media for a short distance, and then disengage as the photon continues on in its original direction after re-forming.

§ When the photon reflects, the horizontal velocity retains its direction, while the vertical velocity of the photon has reversed itself.  This causes a phase reversal when the photon goes from medium of low refraction to a medium of high refraction.  There is no reversal when the photon reflects off a medium transition from high to low Index of Refraction.  

§ The net effect of reflection is to produce a reflected photon that makes an equal angle, incident and exit, compared to a line drawn normal (perpendicular) to the reflecting surface.

o A small increment of energy from the reflected photon is retained by the metal/mirror.  The amount of energy retained by the mirror upon reflecting the photon is held at first by the forward velocity of the electrons the photon has encountered in its collision.  Then as those electrons collide with the nuclei and lattice of the bulk material, the energy is dispersed as thermal energy.

o The amount of energy given to the electrons by the portion of the photon traveling the normal (perpendicular) to the surface of the medium is:

§ Enormal = (Ephoton sinè).  

§ But, in the rebound, that amount of energy will accelerate the mirror to a certain velocity dependent upon its mass.  E = ½ mv².  

§ The velocity of a large mass will be small, but that amount of kinetic energy given to the mirror must be considered in the conservation of energy of the total system.

§ Thus, the rebounded photon will have a lower frequency, and lower energy so as to balance the amount of energy transferred to the mirror.

§ Considering this problem from a conservation of momentum perspective: The photon has rebounded normal to its original direction, and according to the conservation of momentum, the mirror is given an increment of momentum double the magnitude of the momentum of the incoming photon.  

o Non-Metallic reflection: A photon striking a non-metallic substance can be absorbed and captured by the orbital electron system, or some other mode of energy containment such as molecular vibration, atomic rotation, or atomic translation.  

§ If the non-metallic substances do not absorb the incident photons, they will reflect or refract the remaining photons.

§ When refracted or absorbed, both parallel and perpendicular energy components of the photon penetrate the medium. In the case of non-metallic reflection, the surface atoms do not absorb or transmit the incoming photon.  

o At all angles, horizontally polarized light reflects to some extent off of a non-metallic, visible light-transparent air-glass or air-water interface.

o But, vertically polarized light does not reflect at all at the Brewster angle.  Thus, there is some effect in play, some aspect of the photon, which is contributing to reflection that is not operating when the photon is incident with only horizontally polarized light.  

o At the Brewster angle (around 60 from vertical for water), vertically polarized light transmits fully/totally/completely into the refracting media.  Possibly this is because the photon is polarizing the media and penetrating into it with the vertically polarized aspect of the photon.  Thus, an aspect of the photon-media interaction that produces a reflection appears to be how deeply the photon polarizes the substance below its surface layer, angle of the polarization of the media, and the angle of the bonds at the surface of the media.  

o The metallic media is populated with conduction band electrons, which are in general capable of reacting against the photon-applied accelerating force.  And, because there are no gaps in the conduction band, there is no significant transmission, or absorption at any frequency.  Thus, the metal will reflect all frequencies of visible photons, and in general reflect a higher percentage of those photons at all angles.

o When randomly polarized light hits the interface at the Brewster angle, at about 60 from vertical, all the vertically polarized light is refracted into the water.  This leaves only horizontally polarized light as the constituent of the reflected light beam.   Thus, sunglasses that block horizontally polarized light will reveal a glare-free view of the surface of the water at that angle.

o Polaroid material is composed of plastic with long molecules drawn so that the molecules are arranged side by side, all pointing in one direction.  When the E field of the photon vibrates in the same direction as the molecule in the Polaroid film, the energy of the photon is absorbed and does not transmit through that Polaroid material.  Thus, when the Polaroid film, and its constituent long molecules are oriented horizontally, it will block horizontally polarized photons.  Vertically polarized photons will pass through these molecules because there is no current induced that can flow a distance and dissipate the energy by the collision of the electrons.  

o Thus, Polaroid sunglasses will block horizontally polarized photons that reflect off the water at the Brewster angle, and there will be no glare/reflection off the water at that angle.  At he Brewster angle, the vertically polarized photons do not reflect because they are refracted into the water, and the Polaroid film of the sunglasses will block the horizontal photons.  The randomly polarized photons (other than vertical and horizontal) will still be reflected and transmit through the sunglasses.