Microscopy

• How does a light microscope?

  Specimens are illuminated with light, which is focused using a glass lens and viewed with the eye or photographic film
• Do specimens need to be living or dead for Light Microscopy?

  Either - but they might need to be stained with dye to make them visible
• What can you see with specific stains?

  DNA, Lipids, Cytoskeleton
• What resolution do Light Microscopes have?

  200nm - good enough too see cells but not its organelles
• How does an Electron Microscope work?

  Uses beams of electrons to "illuminate" the specimen - electrons bounce off the specimen and onto a phosphor screen, which is then interpreted by a computer and displayed on a monitor
• Does the specimen have to be living or dead?

  Dead - the specimen has to be fixed in plastic and viewed in a vacuum
• Why must the specimen be stained?

  To stop it from being damaged and to obstructed to view due to the beams of electron being shone at it
• How does a TEM work? (Transmission Electron Microscope)

  Pass a beam of electrons through - the ones that do hit a fluorescent screen are detected, and then displayed on a computer screen
• What is needed for TEM?

  Thin slices of specimen so beams of electrons can pass through and create an image
• TEM Microscopes are the most common and have the best resolution
• TEM creates 2D images
• What is the max magnification of a TEM?

  500000x
• How does a SEM work? (Scanning Electron Microscope)

  The specimen is coated in a heavy metal, so the beams of electrons reflect and hit a fluorescent screen which creates an image
• What can now be seen with a SEM?

  Larger, thicker structures and 3D images of specimens
• What is the downside to the SEM?

  Has a lower resolution than the TEM
• What is the max magnification of a SEM?

  100000x
• What is the max resolution of a TEM?

  0.1nm
• What is the max resolution of a SEM?

  10nm
• What can’t you see with an optical (light) microscope?

  Cell Membrane

  DNA Helix
• What is Resolution?

  The minimum distance apart that two objects can be in order for them to appear as separate items
• What is Magnification?

  How many times bigger the image is when compared to the object
• Why does an Electron Microscope have a better Resolution than an Optical Microscope?

  • The Electron Microscope uses beams of electrons
  • Which has a much smaller wavelength than light