Q:

What is the depth of field in microscopy?

A:

Quick Answer

In microscopy, the depth of field refers to the range of distance that runs parallel to the optical axis where the specimen can move and still be viewed without negatively affecting the clarity of the object under observation. The depth of field determines the vertical extent of the plane of focus, which is typically measured in microns.

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Full Answer

In various scientific fields, a microscope is an important tool in viewing and examining objects that are too small to be seen by the naked eye. One of the basic components of a microscope is an eyepiece or ocular lens. A nosepiece, which has several objective lenses is located below the eyepiece. The objective lenses are calibrated into different levels of magnification. Depending on what magnification the specimen is to be viewed, the nosepiece can be easily rotated and the objective lens set into place. Other parts include a mechanical stage, substage condenser, iris diaphragm, substage illuminator, a rheostat and two knobs that are adjusted to focus the sample specimen.

When viewing an object, the overall magnification is calculated by multiplying the value of the ocular lenses with the value of the objective lenses. The total magnification is indirectly proportional to the depth of field. As magnification increases, the axial resolving power of an objective, which is the depth of field, is reduced.

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Related Questions

  • Q:

    What are disadvantages of light microscopes?

    A:

    Light microscope disadvantages include limited resolution, lower magnification and poorer surface view of the specimen. Compound light microscope require the user to adjust to optical inversion, meaning the specimen will appear to be displaced in the opposite direction it is moved.

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  • Q:

    What is a diaphragm on a microscope?

    A:

    A diaphragm on a microscope is the piece that enables the user to adjust the amount of light that is focused under the specimen being observed. A diaphragm is typically found on higher-power microscopes versus less expensive or toy models.

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  • Q:

    How does a light microscope work?

    A:

    A light microscope uses a focused beam of visible light to magnify objects for observation. It works in a similar way as a refracting telescope but with several minor differences. A telescope uses a large objective lens, because it needs large amounts of light to bring a dim, distant object to a bright focus. On the other hand, a light microscope does not need a large objective lens because it only needs to acquire light from a small area of a thin, close specimen that is well illuminated.

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    What makes an egg float?

    A:

    Whether or not an object, such as an egg, floats is a function of its density relative to the medium it's submerged in. Objects that are less dense than their surroundings are buoyant and float. Objects that are denser than their surroundings sink.

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