Microscopy

• Why are microscopes important for biology?

  They allow us to see things that are not visible to the naked eye.
• What are the main types of microscopes and their functions?

  • Light microscopes: Use light and lenses to magnify specimens, allowing us to see individual cells and large subcellular structures.
  • Electron microscopes: Use electrons to form images, providing much higher magnification and resolution.
• How do electron microscopes differ from light microscopes?

  Electron microscopes use electrons instead of light to form images.
• What do light microscopes allow us to see?

  Individual cells and large subcellular structures like nuclei.
• What is the advantage of using electron microscopes?

  They have much higher magnification and resolution than light microscopes.
• What does resolution refer to in microscopy?

  Resolution is the ability to distinguish between two points.
• What can electron microscopes allow us to see in detail?

  Internal structures of mitochondria and chloroplasts, as well as ribosomes and plasmids.
• How do you calculate magnification using a formula?

  • Formula: magnification = image size / real size
  • Rearranged: image size = magnification × real size
  • Ensure image size and real size are in the same units.
• If a specimen is 50 μm wide and magnified at ×100, what is the image size?

  The image size is 5000 μm.
• What is the purpose of a microscope slide?

  To mount a specimen for viewing under a microscope
• What is the final image size in mm if the specimen is 50 μm wide under ×100 magnification?

  The final image size is 5 mm.
• What should you do after cutting up an onion to prepare a slide?

  Use tweezers to peel off some epidermal tissue
• Why is iodine solution added to the slide?

  It is a stain used to highlight objects in a cell
• What is the first step in preparing a slide to view onion cells?

  Add a drop of water to the middle of a clean slide
• How can you rearrange the magnification formula to find the real size of an object?

  • Use a formula triangle to cover the unknown.
  • The remaining parts show the formula needed.
  • Rearranged formula: real size = image size / magnification.
• Why is it useful to write numbers in standard form when using microscopes?

  It makes very big or very small numbers more manageable.
• What is a cover slip?

  A square of thin, transparent plastic or glass
• How is the number 0.017 expressed in standard form?

  It can be written as $1.7 \times 10^{-2}$.
• How do you convert a number to standard form?

  Move the decimal point left or right and represent the movement with a power of 10.
• How should you place the cover slip on the slide?

  Stand it upright next to the water droplet and lower it carefully
• What is the first step to look at your prepared slides under a light microscope?

  Clip the slide onto the stage
• How would you express a mitochondrion that is approximately 0.0025 mm long in standard form?

  It can be expressed as $2.5 \times 10^{-3}$.
• Which objective lens should you select first when using a light microscope?

  The lowest-powered objective lens
• What is the significance of the power of 10 in standard form?

  The power of 10 indicates how many places the decimal point has moved.
• What should you do after moving the stage up to just below the objective lens?

  Look down the eyepiece and adjust the stage downwards
• How do you achieve a clear image of the specimen?

  Use the fine adjustment knob to focus
• What should you use to draw your observations under the microscope?

  A pencil with a sharp point
• What should you do if you need to see the slide with greater magnification?

  Swap to a higher-powered objective lens and refocus
• What should your drawing not include?

  Colouring or shading
• How should subcellular structures be drawn in your observations?

  In proportion to each other
• How much space should your drawing take up on the page?

  At least half of the space available
• How should you label the important features of your drawing?

  Using straight, uncrossed lines
• What should you include in your drawing besides the image?

  A title and the magnification used