FRSC 365 Darkfield

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    What type of materials can be observed using darkfield microscopy?

    Transparent, non-absorbing (colorless) materials.

    What is the primary advantage of darkfield microscopy over brightfield microscopy?

    Specimens appear bright against a completely black background.

    How does darkfield microscopy create a hollow cone of light?

    By blocking undeviated rays from the condenser.

    What happens to light rays in darkfield microscopy when they strike the specimen?

    They are refracted, reflected, and scattered into the objective lens.

    What is the appearance of the background in darkfield microscopy when no specimen is present?

    Completely black background.

    What types of specimens are typically used in darkfield microscopy?

    Aquatic organisms, diatoms, yeast, small insects, fibers, crystals, tissue culture, and dust specimens.

    What is a critical factor for achieving good images in darkfield microscopy?

    Using thin specimens to avoid light scattering that degrades the image.

    What type of objectives are typically used with darkfield microscopy?

    Dedicated darkfield objectives designed for high magnification work.

    What are the two types of condensers mentioned for darkfield microscopy?

    Paraboloid and cardioid condensers.

    What is Rheinberg illumination?

    A variation of darkfield microscopy that uses transparent colored filters to contrast specimen and background colors.

    What is the purpose of calibrating the reticle in microscopy?

    To determine the value of each reticle unit for accurate measurements.

    How is the value of each reticle unit calculated?

    Total distance divided by the total number of reticle units within that distance.

    What is the total distance if the stage micrometer shows 100 SMU and each unit equals 10µm?

    1000µm.

    What is an important consideration when using darkfield microscopy?

    Only a fraction of the light is used, so high intensity is important.

    What is the role of the objective in reflected light microscopy?

    It serves as both the condenser and the objective.

    What are Neo objectives in darkfield microscopy?

    Darkfield objectives that can also be used as brightfield objectives.

    What is the effect of bubbles and dirt in darkfield microscopy?

    They can interfere with the image quality.

    What is the purpose of using open aperture and field diaphragms in darkfield microscopy?

    To allow maximum light to enter for better visibility.

    What is the significance of using oil immersion objectives in darkfield microscopy?

    They help achieve higher magnification and reduce chromatic aberration.