Technical Terms Dictionary
The refractive index of a transparent medium is defined as the relationship of the vacuum velocity of light and the velocity of light within said medium. The name derives from the presence of this value in Snell´s Law.
Snell´s Law says that a ray of light will change its direction or break as it passes from one transparent medium to another.
The refractive index is a physical variable that is independent of temperature and medium. As every substance has a different influence on the velocity of light, each transparent medium has its own typical refractive index. In a medium with a refractive index of 1.5 = 3/2, the light´s velocity is 2/3 of the vacuum velocity of light, i.e. 200,000 km/sec.
The fat or oil is put on the prism of a refractometer. After tempering at the determination temperature for 2 minutes, the refraction of light (caused by the change in velocity) can be determined and converted to the refractive index.
Oils and fats have a deviation of 0.00037 per °C.
With the refractive index, variety and purity testing can be done quickly and easily - analyses take no longer than approx. 2 minutes.
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