The Refractive Issue

posted on May 11th, 2005, 8:31 pm

Here is a small exerpt I found while searching the internet.

"To decipher the phenomenon of refraction, we have to go down to the molecular level of substances. Optical density is directly associated with the index of refraction where the more optically dense a substance is, the higher the index of refraction it will have. The optical density of a substance correlates to the speed at which photons propagate through it. The wavelengths of photons (or EM radiation) are on the same scale as the size of the molecules. Because the molecular structure of every substance is unique, the way in which that structure interacts with the photons is also unique. This statement can ultimately conclude that the molecular structure of a substance determines its optical density, thereby determining its angle of refraction."

I seriously dont get this part: "Because the molecular structure of every substance is unique, the way in which that structure interacts with the photons is also unique."

Does anyone mind elaborating on that part? what kind of molecular structure of substances affect light refraciton differently from other molecular structures?? I am at a loss

posted on May 11th, 2005, 9:14 pm

I think the molecular structure issue is the lattice structure of the crystal, or the spacing between atoms in the solid (more fitting for amorphus materials i.e. glass). If I remember correctly, the amount something refracts by will depend on the wavelength/amplitude of the EM wave and the spacing and size of the atoms in the material. For more info, you may want to either google "refraction" or check it out in wikipedia.com. My optics background isn't all that good though, so I'm probably really over simplifying things.

posted on May 11th, 2005, 10:54 pm

Actually refraction is a function of something called the permittivity (symbol epsilon) of a substance, also known as the dielectric constant. It it independent of both frequency and amplitude, although substances tend to be opaque to different spectra of EM. Teflon is a good example, EM in the Terahertz range (optical light) is blocked, but EM in the radio / microwave range (Megahertz to Gigahertz) is refracted (and reflected). The optical index of refraction (symbol n) is proportional to the square root of the relative permittivity of a substance. Air has a relative permittivity (and optical index) of 1, equal to an epsilon of approx. 8.854 E-12 Farad per meter.

Hope this helps

posted on May 11th, 2005, 11:11 pm

I seriously dont get this part: "Because the molecular structure of every substance is unique, the way in which that structure interacts with the photons is also unique."

In other words, think of it like this: Since all of us are unique in same way and we all are to do something to a certain object, we would all do it differently, no two of us would do the exact same thing.