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Microscopes

Microscopes. Light microscopes were first developed in the 1500s. One of the earliest inventors of microscopes was the Dutch lens grinder Anton van Leeuwenhoek. “Father of Microscopy”

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Microscopes

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  1. Microscopes

  2. Light microscopes were first developed in the 1500s. • One of the earliest inventors of microscopes was the Dutch lens grinder Anton van Leeuwenhoek. “Father of Microscopy” • His microscopes were mostly single lens magnifiers with a place to attach a specimen. He is credited with producing over 250 different microscopes.

  3. The first compound light microscope was designed by the Jansens in 1590, even before van Leeuwenhoek. • The compound light microscope design allowed biologists to view specimens through a series of two lenses. This gives a greater amount of magnification. The total magnification possible is a product of the two lenses used.

  4. Electron Microscopes: Light microscopes can only produce sharp images of objects when the objects are larger than 0.2 micrometers (2 ten thousandths of a millimeter), or about 1/50th of the diameter of the typical cell.

  5. Electron microscopes focuses a beam of electrons on specimens, and can form images 1000 times smaller than those visible under the light microscope.

  6. How can Electron microscopes see much smaller objects than light? • Light wave lengths are too large for some very tiny objects and do not reflect from them. • Electron beams have much smaller wavelengths and can reflect back from the smaller objects. (Images cannot be viewed directly as with light microscopes.)

  7. Two Major types of electron microscopes: • TEM – TRANSMISSION ELECTRON MICROSCOPE • An electron beam shines through very thin specimens. It produces a two-dimensional image. It can only be used to view dead specimens. (They can magnify 200,000 times.)

  8. SEM – SCANNING ELECTRON MICROSCOPE • An electron beam scans back and forth across the surface of a specimen to provide a three-dimensional imageof the object’ssurface. (They can magnify 100,000 times.) • Images of the electron microscope can be seen on a monitor, rather than directly, as with the light microscope.

  9. THE COMPOUND LIGHT MICROSCOPE

  10. Compound Light Microscope– this microscope uses a beam of light that passes through two lenses to provide an enlarged view of structures that are too small to be seen with the unaided eye. Magnification – this refers to the microscope’s ability to increase an object’s apparent size. Resolution- this refers to the ability of a microscope to show details clearly.

  11. Total Magnification- this is calculated by multiplying the ocular lens x the objective lens over the slide. • scanning lens • (ocular 10x)(objective 4x) = 40x total • low power • (ocular 10x)(objective 10x) = 100x total • high power • (ocular 10x)(objective 40x) = 400x total

  12. Field of View – the area of the specimen that is seen when looking through the ocular lens. As the total magnification increases, the field of view decreases. • Depth of Field – the ability to focus through different depths or “layers” within a specimen. • Parafocal – the characteristic of a microscope that maintains focus when switched to another objective lens

  13. Put away the microscope properly: • 1) Remove your slide • 2) Clean the stage • 3) Lower the stage (Some microscopes only) • 4) Place the lowest power objective in place. • 5) Wrap the cord around the supports on the microscope • 6) Place the cover on the microscope

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