3.9: Glossary

Key Terms and Definitions

• Aperture: The opening in the condenser that regulates the amount of light passing through the specimen. A larger aperture allows more light, potentially improving brightness but potentially reducing contrast.
• Arm: The structural part of the microscope that connects the base to the body tube. Used for carrying the microscope.
• Base: The bottom part of the microscope providing stability and support.
• Body Tube (Head): The cylindrical structure connecting the eyepiece to the objective lenses.
• Bright field Microscopy: The most common type of microscopy, where light passes directly through the specimen.
• Condenser: A lens system located beneath the stage that focuses light onto the specimen. Adjusting the condenser affects brightness and contrast.
• Coarse Adjustment Knob: A large knob used for making large adjustments to the focus, typically used with lower magnification objectives.
• Darkfield Microscopy: A technique where only scattered light from the specimen reaches the objective, resulting in a bright specimen against a dark background. Useful for observing unstained specimens.
• Diaphragm (Iris Diaphragm): An adjustable opening within the condenser that controls the amount of light reaching the specimen. Similar to the aperture, but directly within the condenser.
• Eyepiece (Ocular Lens): The lens at the top of the microscope through which the user views the specimen. Typically 10x magnification.
• Field of View (FOV): The circular area visible through the microscope eyepiece. FOV decreases as magnification increases.
• Fine Adjustment Knob: A smaller knob used for making precise adjustments to focus, especially at higher magnifications.
• Fluorescence Microscopy: A technique that uses fluorescent dyes or proteins to label specific structures within a specimen. The specimen is illuminated with specific wavelengths of light, causing the labeled structures to emit light at longer wavelengths.
• Focusing: the process of moving the lens configuration (eyepiece and objective or digital sensor and objective) in relation to the specimen to achieve a sharp image.
• Illuminator: The light source of the microscope. Can be a built-in lamp or external light source.
• Interpupillary distance (IPD) – in binocular microscopes and stereoscopes, the measurement, or the potential range of adjustment, available between the exit pupils, as measured in millimeters.
• Magnification: The process of enlarging the image of an object. Total magnification is the product of the eyepiece and objective lens magnifications (e.g., 10x eyepiece and 40x objective = 400x total magnification).
• Mount: The preparation of a specimen for microscopic examination, including mounting the specimen on a slide and adding a coverslip if necessary.
• Nosepiece (Revolving Turret): The rotating part that holds the objective lenses.
• Numerical Aperture (NA): A measure of a lens's ability to gather light and resolve fine detail. Higher NA values indicate better resolution.
• Objective Lenses: Lenses with different magnifications (e.g., 4x, 10x, 40x, 100x) located on the nosepiece.
• Parfocal: a microscope that, once focused with one objective, remains in focus when the objective is rotated.
• Phase-Contrast Microscopy: A technique that enhances contrast in transparent specimens by manipulating the phase of light waves passing through the specimen. Useful for observing living cells.
• Resolution: The ability to distinguish two closely spaced objects as separate entities (the level of clarity/detail present in an image). Limited by the wavelength of light used. In digital microscopy, the resolution refers to the amount of pixels on the sensor, and is expressed in MP (megapixels).
• Stage: The platform where the microscope slide is placed.
• Stage Clips: Metal clips on the stage that hold the slide in place.
• Staining: The application of dyes to enhance contrast and visualize specific structures within a specimen.
• Working Distance: The distance between the objective lens and the specimen when the specimen is in sharp focus. Decreases as magnification increases.