Summary of Refractive Index Measurements

In this section, the refractive index is limited to the visible region. Birefringence (a famous example in the human body is the cornea) will be described in a later section. These measurement methods (see Table 1) will be described briefly and the Abbe refractometer, which is a useful device for studying gels, will be discussed in detail. 

The thickness J of a gel film with both surfaces parallel to each other under a microscope with magnification approximately 200 times is measured. 

The movement of the microscope d is determined by focusing onto the top and bottom surface and taking the difference between the two positions. The refractive index of the gel is given by the following equation  

The precision in this case is not high but, when the gel is transparent, it is a convenient method (see Reference [285] for more information). 

A prism is made of a gel with the azimuthal angle a. Determine the difference b between the angle of incidence and refraction. The following equation will give  

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