1: 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 are the two types of light sources that can be found in optical microscopes?

  Lamp and mirror
• What are the lenses above the stage called?

  Objective lenses
• How many objective lenses do most optical microscopes have?

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

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

  Ten times
• What are the two focusing dials on the microscope?

  Coarse focusing dial and fine focusing dial
• What is the first step to use 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 viewing a slide?

  The lowest power objective lens, usually four times
• How do you position the objective lens when starting to view a slide?

  Position it so it 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 close to the slide?

  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 a 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 achieving focus with a lower power objective lens?

  Select a higher power objective lens and adjust the fine focusing dial
• What can be seen when viewing 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, 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 with a ruler
• Where can you find questions related to the required practical on using an optical microscope?

  In the vision workbook
• What are the key parts of an optical microscope and their functions?

  • Stage: Holds the microscope slide
  • Lamp: Provides light to view the slide
  • Objective lenses: Magnify the image (4x, 10x, 40x)
  • Eyepiece: Contains the eyepiece lens with 10x magnification
  • Coarse focusing dial: Adjusts the distance between the lens and slide
  • Fine focusing dial: Brings the image into clear focus
• What is the procedure 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 (4x).
  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 come into focus.
  5. Use the fine focusing dial for a clear focus.
  6. Calculate total magnification and adjust to a higher power if needed.
  7. Draw and label the observed cells with a magnification scale.