microscopy

• How do light microscopes work?

  visible light passes through a specimen and then through glass lenses, which magnify the image
• How do electron microscopes work?

  using a beam of electrons, an image of a specimen is formed
• What are the differences in electron and light microscopes?

  electron microscopes have a higher magnification, a higher resolution, they can be used to see much smaller things - internal structure.
• magnification formula

  Magnification = image size / real size
• How to prepare a slide for a light microscope (practical)

  1) Add a drop of water to the middle of a clean slide

  2) Cut an onion and separate it into layers. Use tweezers and peel of the epidermal layer

  3)Using tweezers place the epidermal layer tissue into the water on the slide

  4)Add a drop iodine solution

  5)Place a cover slip
• Parts of a light microscope

  -eyepiece

  -coarse adjustment knob (large)

  -fine adjustment knob (small)

  -high + low power objective lenses

  -stage

  -light
• How to use a light microscope

  1) clip slide onto stage

  2) select lowest powered objective lens

  3) use coarse adjustment knob to move stage below lens

  4) look through eyepiece - use c.a.k. to put into focus

  5) adjust focus with fine adjustment knob

  6) higher powered objective lens - higher magnification

  refocus
• Things to ensure you do when to draw observations

  - pencil (sharp point)

  - use at least half of space available

  - draw with clear unbroken lines

  - do not shade/colour

  - draw in proportion

  - include title and magnification

  - label the important features