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difference between bright and dark field microscopy

Difference Between Bright And Dark Field Microscopy?

Best Answer: In a darkfield the light is blocked from the center of the field of view. That means everything in the field gets lighting from the side and you see things that refract or reflect the light at you more. In effect it increases the contrast and you see structures that would be hard to see in an evenly illuminated field. The specimens look bright against a dark background.The only difference in the scope is a way to block the light out of the center of the field. It is usually a special lens or diaphragm in the substage condenser but it could be as simple as a circular spot painted on a clear glass filter in the filter holder. If one have the diffraction field of a perfect (or homogeneous) medium, he can see the image of a perturbation, making the perfect field lower or higer. If the homogeneous field is lower but the perturbation image intensity is higer, we have dark field image. When the homogeneous field has hihger intensity and we see the image of pertutbation as local decreasing of the intensity, we have bright field image.

If you are a man of science, you probably love microscopes. Microscopes are useful tools that help us see the unseen. With just our naked eyes, we won’t be able to see the tiniest speck of an organism or the tiniest structure of a nonliving object. The invention of microscopes has led us to discover more of the things in our surroundings. Every time we look at the lenses of microscopes, we are often awed by what they reveal to us.The most common types of microscope are the bright and dark field microscopes. These microscopes are the ones we often use in our biology and laboratory classes. Read on to understand the differences between bright and dark field microscopes.The bright field microscope is considered the most basic type of microscope. Since it can be easily operated, this is the very first type of microscope that students handle. As its name implies, when you observe a specimen under a bright field microscope, the specimen will look dark and its field will look bright.

Most often, the bright field microscope can be termed as a light microscope.Though the bright field microscope covers only basic microscopic investigations, it can be used in discipline areas like microbiology, bacteriology, or other life sciences. It can be used to illuminate and magnify specimens of live cells. But before viewing the specimen under this microscope, you have to apply the staining technique. Most organic specimens are often transparent, so we need a staining material to make them visible under the bright field microscope.On the other hand, a dark field microscope is a kind of microscope that lets its user observe specimens under a completely dark background. The specimen will appear brightly lit against its contrasting dark field. You can easily modify or adjust the settings of your microscope to illuminate the specimens under a dark field.Like the bright field microscope, a dark field microscope is used in various disciplines such as microbiology and bacteriology.

 

It is best used to illuminate unstained specimens with similar refractive values to that of the background. In other words, it is ideal for viewing objects that absorb little light. Among the specimens you can view under the dark field microscope are: aquatic organisms like algae and planktons, live bacteria, insects, yeast, hairs, and many more. Researchers prefer using dark field microscopy when they want to examine the external details of their specimens. When we say “external details,” this includes the outlines, boundaries, edges, or surface defects of the specimen.

Summary:

A microscope is an important tool of researchers as well as microscopy students which helps illuminate and magnify certain specimens.

The bright field microscope can also be termed as the light microscope. It is considered the most basic type of microscope which is why microscopy students are first exposed to handling this type of microscope.

When you view a particular specimen under a bright field microscope, you will observe that the specimen is dark while its background is bright; hence the name bright field microscope.

On the other hand, when you view a particular specimen under a dark field microscope, you will observe that the specimen is bright while its background is dark; hence the name dark field microscope.

Both bright and dark field microscopes can be used in various disciplines such as microbiology, bacteriology, or any other life sciences.

Specimens which are transparent are often stained and observed under a bright field microscope. Specimens which absorb little or no light are kept unstained and observed under a dark field microscope.

These are three different microscopic techniques. Brightfield is the standard technique, which retains the natural colors of the specimen. the specimen appears dark on a bright background. Brightfield is suitable when you want to see the natural colors of the specimen or when you observe stained samples.Bright field microscopy is the conventional technique. It is suitable for observing the natural colors of a specimen or the observation of stained samples. The specimen appears darker on a bright background.Darkfield microscopy shows the specimens bright on a dark background. Brightfield microscopes that have a condenser with a filter holder can be easily converted to darkfield by placing a patch stop filter into the filter holder. The specimens appear brigh, because they reflect the light from the microscope into the objective.Phase contrast microscopy requires special phase contrast objectives and a special phase contrast condenser. This technique is useful for observing unstained specimens that lack a color (eg. bacteria). The optics will convert the differences in refractive index of the specimen into brightness differences.Polarization microscopy also produces a bright specimen on a dark background. It can also be easily improvised with a brightfield microscope. A polarizing filter is placed above the lamp and another one is placed between the specimen slide and the objective. Parts of the specimen will then light up. optically active crystals on the slide will produce nice colors.

 

bright vs dark field microscopy By Picture

 

 

 

 

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