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Refraction index measurement

This page illustrates different microscopic techniques for the estimation of the refractive index of small crystals. The pictures throughout the page show how quartz can be seen in a series of immersion liquids with refraction index around  its ordinary index by using the phase contrast microscopy, the oblique illumination, the Becke line method and the dark field. The use of a monochromator to illuminate the stage of the microscope allows more quantitative determination. The images below also show the appearance of the crystals in monochromatic light with wavelengths around the crossing point between dispersion curves of the solid and the liquid.

Theoretical information about index of refraction measurement and bibliography.

Phase contrast microscopy of quartz in a liquid with a refraction index just equal to the ordinary index of quartz (1.544). Use of a monochromator to demonstrate the properties of phase contrast halo.

Use of the phase contrast method for the measurement of the index of refraction. Quartz crystals in  immersion liquids with n=1.528, n=1.539, n=1.544 and n=1.553.

Use of the oblique illumination method for the estimation of the index of refraction. Quartz crystals in  immersion liquids with n=1.528, n=1.539, n=1.544 and n=1.553.

Use of the Becke line to determinate the index of refraction. Quartz crystals in  immersion liquids with n=1.544 and n=1.553. Illustration of the dark field method for index of liquid equal to quartz small index.