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The phase-plate increases the phase difference to half a wavelength. Destructive interference between the two sorts of light when the image is projected results in the specimen appearing as a dark object.

The Phase Contrast Microscope

The phase contrast microscope is widely used for examining such specimens as biological tissues. It is a type of light microscopy that enhances contrasts of transparent and colorless objects by influencing the optical path of light. The phase contrast microscope is able to show components in a cell or bacteria, which would be very difficult to see in an ordinary light microscope.

Altering the Light Waves
The phase contrast microscope uses the fact that the light passing trough a transparent part of the specimen travels slower and, due to this is shifted compared to the uninfluenced light. This difference in phase is not visible to the human eye. However, the change in phase can be increased to half a wavelength by a transparent phase-plate in the microscope and thereby causing a difference in brightness. This makes the transparent object shine out in contrast to its surroundings.

The Invisible Can Be Seen
The phase contrast microscope is a vital instrument in biological and medical research. When dealing with transparent and colorless components in a cell, dyeing is an alternative but at the same time stops all processes in it. The phase contrast microscope has made it possible to study living cells, and cell division is an example of a process that has been examined in detail with it. The phase contrast microscope was awarded with the Nobel Prize in Physics, 1953.

 Related Laureate:
The Nobel Prize in
Physics, 1953
- Frits (Frederik) Zernike »

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