Abbe refractometer related introduction

The Abbe refractometer is used to measure the optical constant refractive index and average dispersion of transparent, translucent liquids or solids. Through the determination of the refractive index and average dispersion, the optical properties, purity, concentration and dispersion of the material can be known. The instrument can measure the percentage of sugar content in sugar solution. It is a commonly used instrument in petroleum, medicine, food crystal, daily chemical and other industrial departments, schools and scientific research units.

1. Basic principles

Since light travels at different speeds in different media, refraction occurs when monochromatic light passes from one transparent medium to another. At a certain temperature, the ratio of the sine of the incident angle i to the sine of the refraction angle r is equal to the ratio of its propagation speed v ₁ to v ₂ in the two media , and the ratio n, 2 is the refractive index, that is, the refractive index, Right now

When it is qualitative, it bends to the normal line (Fig. 7-14). At a certain temperature, the refractive index n,2 is a constant for two given media, so when the incident angle i increases, the refraction angle r must also increase correspondingly, when i reaches the maximum value π/2 , the resulting refraction angle rc is called the critical refraction angle. Apparently, the light incident on the left side of the normal line in the figure is refracted into the second medium, and the refracted lines should all fall within the critical refracted angle r. At this time, if an eyepiece is disposed at M, half light and half darkness appear on the mirror. It can be seen from formula (7-7) that when a medium is determined, the size of the critical refraction angle r. properties of a medium) have a simple functional relationship.