Required Practical 1: Microscopes

• What should you be able to do by the end of the video?

  Describe how to use an optical microscope
• Why is it important to learn the details of using an optical microscope?

  It could come up in a six mark essay
• What is the main part of the optical microscope where the slide is placed?

  The stage
• What is the function of the lamp in an optical microscope?

  It illuminates the microscope slide
• What is used in some optical microscopes instead of a lamp?

  A mirror
• What are the objective lenses used for in an optical microscope?

  They magnify the specimen being viewed
• How many objective lenses do most microscopes have?

  Three
• What are the typical magnifications of the objective lenses?

  Four, ten, and forty times
• What is the magnification of the eyepiece lens?

  Ten times
• What is the purpose of the coarse focusing dial?

  To adjust the distance between the lens and slide
• What should you do after placing the slide on the stage?

  Select the lowest power objective lens
• Why should you look at the microscope from the side while adjusting the objective lens?

  To avoid damaging the slide
• How do you bring the cells into focus after positioning the objective lens?

  Use the coarse focusing dial
• How do you calculate the total magnification?

  Multiply eyepiece magnification by objective magnification
• What is the total magnification when using a ten times eyepiece and a four times objective lens?

  $40 \text{ times}$
• What should you do after selecting a higher power objective lens?

  Adjust the fine focusing dial
• What can you see when observing animal cells under an optical microscope?

  Nucleus, cytoplasm, and cell membrane
• What additional structures can be seen in plant cells under an optical microscope?

  Cell wall, chloroplasts, and vacuole
• What should you include in your drawing of the cells?

  A magnification scale
• How do you create a magnification scale for your drawing?

  Measure the diameter of the field of view
• What should you write on your drawing besides the scale?

  The magnification used
• What are the steps to use 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 are in focus.
  5. Use the fine focusing dial for a clearer focus.
  6. Calculate total magnification by multiplying eyepiece and objective lens magnifications.
  7. Optionally switch to a higher power objective lens and refocus.
• What limitations exist when using an optical microscope to view cells?

  • Limited detail visible
  • Cannot see organelles like ribosomes
  • Dependent on the type of cell being observed
• What are the key components of an optical microscope?

  • Stage
  • Objective lenses (4x, 10x, 40x)
  • Eyepiece lens (10x)
  • Coarse and fine focusing dials
  • Light source (lamp or mirror)
• What should be included in a drawing made from an optical microscope observation?

  • Clear labeled drawing of cells
  • Magnification scale
  • Magnification value (e.g., 100 times)