MICROSCOPES - lesson 1 Unit 1

Microscopes

• There are 2 types of microscopes:
• Light microscope
• Electron microscope
• Light microscope can't go in too much details. If the magnification is too high, the image won't be as clear. it can't distinguish two pints closer than 200nm.
• Electron microscopes use abeam of electrons instead of light. The microscope is operated in a vaccum.
• Different types of electron microscopes.
• TEM - Transmition Electron Microscope is used to examine thin slices of cells and tissues.
• SEM- Scanning Electron Microscope has a large depth of field. So, it can be used to examine surface structures, (depth of field is the distance between the closest object and the furthest object in a focus) .
• Advantages
• TEMs have a magnification of times 1 000 000. The resolution has a limit of 1nm. The TEM has revealed some structures in cells that a light microscope can't see.
• SEMs have a lower magnification times 30 000. The limits of resolution in a SEM is lower than a TEM with 50nm.
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Folie 2

• Magnification
• Magnification is the ability to make small object seem larger.
• Calculating magnification
• The formula is:
• real size = image size/ magnification
• Calculating using scale bars
• magnification = length of scale line/ length of scale line given
• Converting units
• The first image shows micrometres.
• The second image shows nanometres.
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