The amount of separation is very small, and depends on the thickness of the glass, the index of refraction and the focal length of the telescope.
The refraction of light passing through sea-water is dependent on the salinity to the extent that the index of refraction is greater as the salinity increases.
Sarasin and longer series of experiments by Tornde and Kriimmel this relation is shown to be so close that the salinity of a sample can be ascertained by determining the index of refraction.
The line n shows the factor by which the index of refraction of the transmitted vibration is multiplied, and the curve p the intensity of the absorbed vibration for that wave-length.
The diamond has the requisite optical properties, its index of refraction being about i 6 times as large as that of ordinary glass.
