Pro-Juice - Digital Refractometer Brochure

When light passes from one medium to another, the speed at which the light travels will change depending on the parameters of the materials. This principle can be seen when looking at a straw in a glass or an oarsman on the river, as shown in the diagram. The ratio or change in the speed of light is called refractive index and instruments that measure this are called refractometers. The refractive index of a liquid is related to its concentration and so a refractometer can display the concentration in suitable units, such as °Brix (sucrose), glucose, sodium chloride, urea and urine specific gravity to name just a few.