刻面红宝石及片板红宝石的颜色对比

e-ray和o-ray代表什么含义，无法理解，请高手们指教！

At this point it is interesting to comment on the color of the wafers in comparison to the color that would be seen if a gem had been faceted from them instead. As the diagram below illustrates, the light just travels through the wafer sample without being reflected. Thus to the observer it might look pink owing to the thin nature of the sample. Now in the case of a faceted stone, the color would be more saturated owing to the longer path length followed within the gem... Furthermore the hue would be slightly different resulting from a combination of some o and e-rays produced by total internal reflection within the stone, while for the wafer, if oriented perpendicular to the c-axis, a purer o-ray hue would be observed.