Required Practical 1:Microscopes

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

  Describe using 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?

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

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

  To magnify 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 are the two focusing dials on the microscope?

  Coarse and fine focusing dials
• What is the first step to view a prepared slide using an optical microscope?

  Place the slide onto the stage
• Which objective lens should be selected first for viewing?

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

  Almost touch the microscope slide
• Why should you look at the microscope from the side while adjusting the lens?

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

  Look through the eyepiece
• What is the purpose of the fine focusing dial?

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

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

  Forty times
• What should you do after selecting a higher power objective lens?

  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
• How do you include a magnification scale in your drawing?

  Measure the diameter of the field of view
• What should be included in the drawing of cells?

  A magnification scale and labels
• Where can you find questions on this required practical?

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

  1. Place the slide on the stage.
  2. Use clips to hold the slide.
  3. Select the lowest power objective lens.
  4. Position the lens near the slide.
  5. Look through the eyepiece.
  6. Adjust the coarse focusing dial.
  7. Use the fine focusing dial for clarity.
  8. Calculate total magnification.
  9. Draw and label the cells.
• What are the limitations of viewing cells with an optical microscope?

  • Limited detail visible
  • Cannot see organelles like ribosomes
  • Dependent on cell type and preparation