Refractive index
Laboratory > Optical
| Refractive index | |
| ASTM D 542 - ISO 489 | |
The optical properties are related to both the degree of crystallinity and the actual polymer structure. The refraction of a wave is the flexion it suffers when it enters a medium with different propagation velocity. The refraction of the light, when it passes from a rapid propagation medium to a slower one, doubles the ray of light in the normal direction to the contact surface between both media. The amount of diffraction depends on the refractive indices of the two media. It is symbolized by the letter "n" and it is a dimensionless value: where: c = the speed of light in a vacuum v = speed of light in the medium whose index is calculated (water, glass, etc.) n = index of refraction of the medium. The refractive index, n, is directly related to the electronic polarizability that depends on the polar moment induced by the radiation. Polymers that have a similar chemical structure (C-C bond chains) have refractive indices similar to about 1.5, and for all organic polymers 1.33 <n <1.73. When the light falls on a sample part is reflected, part can be absorbed, part can be scattered and the remaining fraction will be transmitted. |   |