The Microscope
Why do we use a microscope? Many things are smaller than we can see with the naked eye. To accurately study Biology we need a tool to help us see these tiny things.
History Antony van Leeuwenhoek is credited with developing the first microscope in about Although the compound microscope was already in use, what made Antony’s invention special was that he was able to magnify his ‘wee beasties’ by up to 270X. Antony was the first to see bacteria, red blood cells, yeast and so much more!
Types of Microscopes Binocular scopes allow you to see in 3D. Binocular Compound Microscope –A compound microscope is one that has two lens, usually one in the eyepiece and another that can be varied. –These have a magnification of up to 1000X. –We use binocular scopes in our lab.
Stereo Microscope –A stereo microscope has a magnification of about 10 X. –With a stereo microscope you can look at the details of larger objects. For example, an entire leaf or the whole body of a spider.
Monocular Compound Microscope –A monocular microscope has just one eyepiece to look through. –Most students find this type of scope more challenging to use.
Electron Microscopes Objects smaller than 0.2 um can be seen with an electron microscope. (Viruses, internal cellular structures)
Scanning Electron Microscope –Image appears in 3-dimensions and in black and white. The magnification is usually 1000X to 10,000X. It is particularly useful for studying the surfaces of cells and viruses.
Scanning Electron Microscope
Weevil, 75X Mosquito head, 200X
Red blood cells, color enhanced
Transmission Electron Microscope The item to be viewed is sliced into very thin slices, the image is a slice of the cell. These images are used to cross sections of cells and their intracellular structures. Magnification can be as much as 10,000X to 100,000 X.
Sperm cross section TEM, Mycobacterium tuberculosis TEM
Know the following Microscope parts and their function. Eyepiece Ocular lens Nosepiece Objective lens Stage Stage clip Light switch Light intensity knob Fine adjustment Coarse adjustment Stage manipulator knobs Condenser Light source Iris diaphragm knob Cord holder Microscope body
Ocular Lens The ocular lens has a 10X magnification.
Objective Lens There are four objective lenses. Red – 4X Blue – 10X Yellow – 40X Oil immersion (white) – 100X
Total Magnification When the image travels through the objective lens and the ocular lens it magnifies the magnification of the objective lens by 10X. Ocular lens Objective lens Total magnification 10XRed 4X 40X 10XBlue 10X 100X 10XYellow 40X 400X 10XWhite 100X 1000X
The proper way to carry your microscope. Always carry the microscope with two hands, holding it close to your body.
Improper carrying. Carrying the microscope like this could result in your ruining a $ piece of equipment. This will not score you brownie points with your instructor!
Proper usage At the lab table, unwrap only as much cord as you need, the rest should remain stored around the cord wrap.
The microscope should always be stored with the 4X (red) lens in place and the stage in its lowest position.
Always store your microscope in its numbered position, with the dust cover in place.
How to focus your image Place the slide on the stage, held in place by the stage clip. ALWAYS start with the 4X lens. Focus your image. Move to the 10X lens, focus. NEVER use the coarse focus higher than 4X. Repeat at the 40X lens, focus using the fine focus.
Distance between lens and slide Use only the fine focus knob with the 40X and 100X lens.
The Oil Immersion Lens The oil immersion lens or 100X lens is used with special optical oil. It makes the image clear at a higher magnification Your instructor will tell you if you need to use this lens. It is important to remove all the oil if you use the oil immersion lens.
Cleaning Please use only lens paper to clean the lenses, never paper towels or Kimwipes. Never use dry lens paper to clean eyepieces. Use the cleaning solution provided or breathe on the surface to be cleaned, then wipe.