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An object may be not transparent either because it reflects the incoming light or because it absorbs the incoming light. Almost all solids reflect a part and absorb a part of the incoming light. When light falls onto a block of metal , it encounters atoms that are tightly packed in a regular lattice and a " sea of electrons " moving randomly ...
Phase-contrast microscopy is particularly important in biology. It reveals many cellular structures that are invisible with a bright-field microscope , as exemplified in the figure. These structures were made visible to earlier microscopists by staining , but this required additional preparation and death of the cells.
An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general, some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction).
A transparent object allows light to transmit or pass through. Conversely, an opaque object does not allow light to transmit through and instead reflecting or absorbing the light it receives. Most objects do not reflect or transmit light specularly and to some degree scatters the incoming light, which is called glossiness .
Another important advantage of the technique is that it allows transparent objects to be seen very clearly. This is because it is sensitive to the phase of the radiation that has passed through a specimen, and so it does not rely on the object absorbing radiation. In the case of visible-light biological microscopy, this means that cells do not ...
Rheinberg illumination is a variant of dark field illumination in which transparent, colored filters are inserted just before the condenser so that light rays at high aperture are differently colored than those at low aperture (i.e., the background to the specimen may be blue while the object appears self-luminous red). Other color combinations ...
In biology, it is employed in viewing unstained biological samples, making it possible to distinguish between structures that are of similar transparency or refractive indices. [ citation needed ] In geology, phase contrast is exploited to highlight differences between mineral crystals cut to a standardised thin section (usually 30 μm ) and ...
Tissue clearing refers to a group of chemical techniques used to turn tissues transparent. [1] [2] [3] By turning tissues transparent to certain wavelengths of light, it allows one to gain optical access to a tissue. [1]