microscopy

• what are cells studied using?

  microscopes
• what do microscopes do?


  allow us to see things that we can't with the naked eye
• what do light microscopes do?


  use light and lenses to form an image of a specimen and magnify it, they let us see individual cells and large sub-cellular structures, like nuclei
• what do electron microscopes do?


  use electrons instead of light to form an image, have a much higher magnification than light microscopes
• what is resolution?


  the ability to distinguish between 2 points, a higher resolution gives a sharper image
• which microscope has a higher resolution?

  electron
• what are examples of what can be seen under an electron microscope?

  smaller things in more detail, like the internal structure of mitochondria and chloroplasts, even tinier things like ribosomes and plasmids
• what is the formula for magnification?


  magnification = image size / real size
• what is the first step of using a microscope?

  put a specimen on a microscope slide, a slide is a strip of clear plastic onto which the specimen is mounted
• how do you prepare a slide to view onion cells?

  • add a drop of water to middle of clean slide
  • cut up onion and separate into layers, use tweezers to peel off epidermal tissue from the bottom of a layer
  • place epidermal tissue into water on the slide using tweezers
  • add a drop of iodine solution
  • place cover slip on top
• how do you use a light microscope to look at your slide?

  • clip slide onto the stage
  • select the lowest-powered objective lens (lowest magnification)
  • use coarse adjustment knob to move stage up to just below lens
  • look through eyepiece, use adjustment knob to move stage downwards until image is roughly in focus
  • adjust focus until you get clear image of what is on the slide
  • swap to a higher-powered objective lens and refocus if you need a greater magnification