Required Prac 1 : Microscopes

• What is the purpose of using an optical microscope in biology?

  To observe cells on a prepared microscope slide.
• What are the main components of an optical microscope?

  • Stage
  • Light source (lamp or mirror)
  • Objective lenses (usually three)
  • Eyepiece lens
  • Coarse focusing dial
  • Fine focusing dial
• Why is it important to learn the details of using an optical microscope?

  Because it is a required practical that may appear in exams.
• What is the function of the stage on an optical microscope?

  To hold the microscope slide in place.
• How does light pass through the microscope slide?

  Light passes up through the microscope slide.
• What are the typical magnifications of objective lenses in an optical microscope?

  Four times, ten times, and forty times.
• What is the purpose of the eyepiece lens in an optical microscope?

  To magnify the image viewed through the microscope.
• What is the process for using an optical microscope to view a prepared slide?

  1. Place the slide on the stage and secure it with clips.
  2. Select the lowest power objective lens (usually four times).
  3. Position the objective lens close to the slide using the coarse focusing dial.
  4. Look through the eyepiece and adjust the coarse focusing dial until cells come into focus.
  5. Use the fine focusing dial for a clearer focus.
  6. Calculate total magnification by multiplying eyepiece and objective lens magnifications.
• What should you do after selecting a higher power objective lens?

  Adjust the fine focusing dial to bring the cells back into focus.
• How do you calculate the total magnification of an optical microscope?

  By multiplying the eyepiece magnification by the objective lens magnification.
• What cellular structures can be observed in animal cells using an optical microscope?

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria (limited detail)
• What cellular structures can be observed in plant cells using an optical microscope?

  • Cell wall
  • Cytoplasm
  • Nucleus
  • Vacuole
  • Chloroplasts (depending on the type of plant cell)
• How do you create a magnification scale for a drawing made from an optical microscope observation?

  By measuring the diameter of the field of view with a ruler and including a scale bar in the drawing.