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Microscopy and Cytology - General Biology lab 5

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Terms in this set (20)

  • Function of the arm on a compound microscope
    Used to carry the microscope; located between the body tube and the base.
  • Purpose of the condenser in a compound microscope
    Substage lens that concentrates light on the specimen; its position can be adjusted to vary light intensity.
  • What is total magnification in microscopy?
    The product of the ocular lens magnification and the objective lens magnification.
  • Magnification of the ocular lens in the lab microscopes
    10X; the eyepiece magnifies the image ten times.
  • Magnifications of the four objective lenses used
    Scanning: 4X, Low power: 10X, High power: 40X, Oil immersion: 100X.
  • How to calculate total magnification with a 40X objective lens
    Total magnification = 10X (ocular) × 40X (objective) = \(400X\).
  • Definition of resolution in microscopy
    Resolving power is the ability to distinguish two close objects as separate; compound microscopes resolve objects about 0.2 µm apart.
  • What is parfocal in compound microscopes?
    Once focused on low power, the image remains nearly in focus when switching to higher magnifications.
  • Proper use of coarse and fine focus knobs
    Use coarse focus only on low power; use fine focus for final adjustments and on high power.
  • Function of the iris diaphragm
    Regulates the amount of light passing through the stage to improve image contrast.
  • What is the field of view in microscopy?
    The circular area visible through the microscope lens; its diameter decreases with increasing magnification.
  • What is depth of field in microscopy?
    The vertical distance in focus; decreases as magnification increases.
  • How to prepare a wet mount slide
    Place specimen on slide, add liquid (water or stain), cover with coverslip avoiding air bubbles, then observe under microscope.
  • Purpose of staining specimens
    Stains absorb light and improve contrast to reveal cellular structures.
  • Ocular micrometer calibration at low power (10X objective)
    One ocular unit equals \(10\ \mu m\).
  • Ocular micrometer calibration at high power (40X objective)
    One ocular unit equals \(2.5\ \mu m\).
  • How to measure specimen size using an ocular micrometer
    Count ocular units spanning the specimen and multiply by the ocular unit length for the objective used.
  • Difference between red and white blood cells under microscope
    Red blood cells are small, round, pinkish, and lack a nucleus; white blood cells are larger with dark-stained nuclei.
  • Why never use coarse focus on high power
    Coarse focus can damage the slide or lens because the objective is very close to the specimen.
  • How to carry a microscope safely
    Use both hands: one on the arm and one under the base; keep the cord secure to avoid tripping.