cell biology : required practicle - microscopes

• What should you be able to do by the end of the video on using an optical microscope?

  Describe how to use an optical microscope to look at cells on a prepared microscope slide
• Why is it important to learn the details of using an optical microscope?

  It is a required practical that could come up in the exam as a six mark essay question
• 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 provide light that passes up through the microscope slide
• What do some optical microscopes use instead of a lamp?

  A mirror to reflect light
• What are the lenses above the stage called?

  Objective lenses
• How many objective lenses do most microscopes have, and what are their typical magnifications?

  Three objective lenses with magnifications of four times, ten times, and forty times
• What is the magnification of the eyepiece lens?

  Ten times
• What are the final parts of the microscope mentioned in the video?

  The coarse focusing dial and the fine focusing dial
• What is the first step in using an optical microscope to view a prepared slide?

  Place the slide onto the stage and use the clips to hold it in place
• Which objective lens should be selected first when using an optical microscope?

  The lowest power objective lens, usually four times
• How do you position the objective lens when using an optical microscope?

  Turn the coarse focusing dial until the objective lens almost touches the microscope slide
• Why is it important to look at the microscope from the side while adjusting the objective lens?

  To avoid damaging the slide
• What should you do after positioning the objective lens?

  Look down through the eyepiece and slowly turn the coarse focusing dial
• What is the purpose of the fine focusing dial?

  To bring the cells into clear focus
• How do you calculate the total magnification of the microscope?

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

  $40 \text{ times}$
• What should you do after calculating the total magnification?

  Select a higher power objective lens and adjust the fine focusing dial
• What can you see when looking at animal cells under an optical microscope?

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

  The cell wall, cytoplasm, nucleus, vacuole, and chloroplasts
• What should you include in your drawing of cells observed under the microscope?

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

  Measure the diameter of the field of view in millimeters and show this on the drawing using a scale bar
• What should you write on your drawing besides the scale?

  The magnification, for example, 100 times
• Where can you find questions related to the required practical on using an optical microscope?

  In the vision workbook
• What are the steps to use an optical microscope to view a prepared slide?

  1. Place the slide onto 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 slowly turn the coarse focusing dial to bring cells into 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.
  8. Draw the cells with labels and a magnification scale.