Use electrons instead of light to form images.

Light Microscopes

Light Microscopes
• Unknown when first invented, but probably between 1590-1610 A.D.
• Can magnify up to 1000 x
• Shines light through an object and projects the image through a series of lenses that magnify the image.
• Relatively inexpensive

Uses
• Great for studying live microscopic organisms.
• Great for studying cells and tissues in general.
• Widely used in hospitals and clinics to diagnose disease.

Example images using light microscopes

Example images using light microscopes

Example images using light microscopes

Transmission Electron Microscope
(TEM)

Transmission Electron Microscope
(TEM)
• First invented in 1931 (in Germany)
• Can magnify up to 200,000 x (and beyond)
• Similar to a light microscope except that a beam of electrons is used instead of light. The electrons that penetrate through the object and create an image which is then enlarged and then viewed on a computer monitor.
• Samples of the object must be sliced very thin before using the TEM. (No living specimens.)
• Very expensive and time consuming to prepare slides.

Uses of the TEM
• Used in biological/medical research to investigate parts of cells and molecules.
• Used in material science to study the structure and the weaknesses of crystals.
• Used in nanotechnology.

Example images using TEMs

Example images using TEMs

Example images using TEMs
Nanotubes

Example images using TEMs
Marburg virus

Scanning Electron Microscope
(SEM)
• http://www.mos.org/sln/SEM/

Scanning Electron Microscope
(SEM)
• First invented in 1942
• Can magnify typically up to 10,000 x
• Gives a 3D image of the surface of the object
• Again, a beam of electrons is used instead of light. The electrons that bounce off the object create the image. The microscope scans a certain region of the object multiple times and then combines multiple images to create what we then see on a computer monitor as one 3D image.
• No slicing needed so easier to prepare samples.
Larger objects can be viewed.
• Very expensive.

Uses of the SEM
• Multiple uses - for viewing the surface of any microscopic object.
• Insect parts
• Bacteria
• Food industry
• Material science
• Education
• Art

Example images using SEMs
•Mascara brush

Example images using SEMs
• Moth antennae

Example images using SEMs

Practice Quiz
• Now look at the following images.
Determine which type of microscope produced each image and write your answers down on a piece of paper.
• LM = Light Microscope
• TEM = Transmission Electron Microscope
• SEM = Scanning Electron Microscope

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Mosquito

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