Glass Sphere in Matching Refractive Index Liquid When Viewed With Monochromatic Light at the Matching Wavelength

Transmitted Brightfield Illumination, Monochromatic Light, D-Line (589 nm)

Definition/Function:

Objects are only visible if their refractive index is different than that of the medium that surrounds them. If a particle and the liquid that it is mounted in match in refractive index for some wavelength and only that wavelength of light is used to view the particle then the interface between the particle and the liquid disappears. Structure inside the particle that has a refractive index different than the particle becomes easily visible.

Conditional Requirments:

The particle is mounted in a liquid of matching refractive index and viewed with monochromatic light at the wavelength for which the particle and liquid match most precisely.

Microscope Configuration:

Characteristic Features:

This is a very useful technique to examine the internal structure of transparent materials. One example would be to examine the fine structure of the medulla of a hair. Mounting the hair in a refractive index medium of about 1.555 minimizes interference of the surface cuticle pattern.

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