PX154 - I4 - propagation of light
waves, wave fronts, and rays
- rays: show the direction of propagation at
to the wavefronts
light in matter: refractive index
- light travels though matter via a continual process of scattering by the electrons in the material
- the scattering of the wavefronts produces "wavelets" which sum to create the new wavefront. hence, the light propagates through the material
- the scattering process effectively slows the light down
- the refractive index,
, is defined as as:
where,
- eg:
| material | |
|---|---|
| glass | |
| diamond | |
| water | |
| air | |
| "bose-einstein condensate" | |
| aluminium (x-ray) |
- for bose-einstein condensate,
- for aluminium, and in real situations, group velocity is what matters and