Indian Fashion shadi Jewellery Collection 35

Indian shadi Jewellery. 
By Aamir Mannan.
10.REFRACTIVE INDEX AND ITS MEASUREMENT

If therefor in any two media which are in optical contact we can measure the angle where total reflection beings (i.e. the critical angle), and we known the refractive index of the denser medium. it is possible to calculate the refractive index of the rarer medium. this is the underlying principle of all total 

reflection refractometers (sometimes called total refractometers), but in the instruments designed for gem testing all calculation is ingeniously avoided. In such refractometer the optically dense medium of known refractive index is in the form of polished hemisphere of heavy lead glass, or a segment of such a hemisphere, or a truncated 60o prism of the same material, the flat upper surface in each case forming the 'table' of the instrument. if the flat, polished surface of any gemstones of lower refractive index than the hemisphere is place in optical contact with this table, rays passing through the glass to the stone will be mostly

refracted into the stone, and thance escape into the air, when they strike the surface at less than the critical angle, but totally reflected back from the surface of the stone when they strike at an angle exceeding the critical angle.