Microscopy

• How many types of microscope are there?

  2
• What are the two types of microscope?

  Light Microscopes and Electron Microscopes
• What does a light microscope use to magnify an image ?

  Light and Lenses
• What can we see with a light microscope?

  Individual cells and large subcellular structures, such as nuclei.
• What do electron microscopes use to form an image?

  Electrons
• What is resolution?


  The ability to distinguish between two points. (A higher resolution therefore gives a sharper image)
• How are electron microscopes better than light microscopes?

  Much higher magnification and higher resolution
• What can we see with a electron microscope that we cant with a light microscope?

  Smaller things like the internal structure of mitochondria and chloroplasts . And even smaller things such as ribosomes and plasmids.
• What is the formula for Magnification?

  Magnification = Image Size / Actual Size

  (I AM triangle)
• How many micrometres in one millimetre?

  1000 micrometres in one millimetre
• Ensure knowledge of names of light microscope components

  
• How do you prepare a slide?

  1. Add a drop of water to the middle of a clean slide
  2. (For an onion) Cut an onion and separate into layers. Use tweezers to peel off some epidermal tissue from the bottom of one layer.
  3. Using the tweezers, place the epidermal tissue into the water on the slide.
  4. Add a drop of iodine solution.
  5. Place a cover slip on top.
• What is iodine solution and why do we use it when preparing a slide?

  Iodine solution is a stain. We use it to highlight objects in a cell by adding colour to them.
• How do you place a cover slip onto a slide?

  Stand the cover slip upright next to the water droplet. Then, using tweezers, gently lower it.
• Why do we place a cover slip gently on a slide?

  To ensure there are no air bubbles which will obstruct the view of the specimen.
• How do you use a light microscope to look at your slide?

  1. Clip the prepared slide onto the stage
  2. Select the lowest powered objective lens
  3. User the coarse adjustment knob to move the stage up to just below the objective lens. Look from the side.
  4. Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards, until the image is roughly in focus.
  5. Use the fine adjustment knob, until you get a clear image of the specimen.
  6. If you need to see with a greater magnification swap to a higher powered objective lens and repeat.
• How do you draw your Observations of a specimen through a microscope?

  • Use a pencil with a sharp point
  • Draw with clear unbroken lines
  • Ensure drawing takes up at least half the space available
  • Do not include shading or colouring
  • If drawing cells, the subcellular structures should be drawn in proportion
  • Include a title of the specimen and write the magnification it was observed under
  • Label the important features of the drawing (e.g. chloroplasts and nuclei) with straight unbroken lines
• How can you Measure the size of a single cell under a microscope?

  1. Place a clear ruler on top of the microscope slide. Clip the ruler and slide onto the stage.
  2. Select the objective lens that gives an overall magnification of X100.
  3. Adjust the focus to get a clear image.
  4. Move the ruler so the cells are lined up along 1mm. Then count the number of cells in the 1mm sample.
  5. 1mm = 1000 micrometres. Therefore, to calculate the length of an individual cell divide 1000 micrometres by the number of cells in the sample
• What is the calculation for working out the length of a scale bar for microscopy diagrams?

  Scale Bar Length (micrometres) = Drawn length of cell (Micrometres) / Actual Length of Cell (Micrometres)
• What is this symbol. µm

  Micrometre
• How many µm = 1 mm?

  1000