Required Practical 1: Microscopes

• 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?

  To illuminate 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?

  To magnify the image of the specimen
• 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
• Why should you look at the microscope from the side while adjusting the objective lens?

  To avoid damaging the slide
• What should you do after placing the slide on the stage?

  Select the lowest power objective lens
• How do you bring the cells into focus after selecting the lowest power objective lens?

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

  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 might you see when observing plant cells under an optical microscope?

  Cell wall, cytoplasm, and nucleus
• What should you include in your drawing of cells?

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

  Measure the diameter of the field of view
• What are the steps to use an optical microscope to view a prepared slide?

  1. Place the slide on the stage and secure it.
  2. Select the lowest power objective lens.
  3. Position the 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 magnifications.
  7. Optionally switch to a higher power objective lens and refocus.