Dark-field microscope

Dark-field microscopy is a microscopy technique that enhances the contrast in unstained samples by illuminating the sample with light that will not be collected by the objective lens and thus will not form part of the image. This produces the classic appearance of a dark, almost black, background with bright objects on it.

Principle

The principle of dark-field microscopy is based on light scattering. The added light is scattered by the specimen and then collected in the microscope objective. This scattered light forms the image while the directly transmitted light is omitted. The resulting image is a light silhouette of the specimen on a dark background.

Applications

Dark-field microscopy is widely used in the study of marine organisms, such as plankton, and also in the observation of living cells and tissues. It is also used in the detection of bacteria, viruses, and other small particles.

Advantages and Disadvantages

The main advantage of dark-field microscopy is that it allows the observation of specimens that are invisible or hard to see in normal light microscopy, such as transparent, colorless, or non-absorbent specimens. However, it also has some disadvantages. For example, it is not suitable for thick or highly pigmented specimens. Also, the high contrast can make it difficult to distinguish details within the specimen.

See Also

• Microscopy
• Light Microscopy
• Phase Contrast Microscopy
• Fluorescence Microscopy

References

Dark-field microscope Resources
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