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16 Cards in this Set
- Front
- Back
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When were microscopes first invented?
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around 1590
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What type of microscopes were used by Renaissance scientists?
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light microscopes
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What types of lenses are contained in a light microscope?
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ocular lens, objective lens, and a condenser lens.
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Besides the lenses, what is the other important component of a light microscope?
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a light source
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What is magnification?
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the ratio of an object's image to its real size.
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What is resolution?
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the measure of clarity of the image; it is the minimum distance two points can be separated and still be distinguished as two separate points.
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What is the maximum resolution of a light microscope?
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0.2 micrometer (um) or 200 nanometer (nm)
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Using the maximum resolution of a light microscope, what is the smallest living organism that can be seen?
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a small bacterium
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What is the limiting factor in light microscope resolution?
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the shortest wavelength of light used to illuminate the specimen.
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What is the maximum resolution of a light microscope?
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about 1,000 times the size of the actual specimen
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What happens to the image in a light microscope if the magnification is increased beyond the maximum 1,000x?
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the image becomes increasingly more blurry
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What is the main difference between a light microscope and an electron microscope?
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Where a light microscope uses light, the EM focuses a beam of electrons through or onto the specimen.
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What is the main advantage of using a beam of electron rather than light in a microscope?
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The wavelength of an electron beam is much shorter than the wavelength of visible light.
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What is the maximum resolution of an electron microscope?
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Theoretically, about 0.002 nm, but the practical limits for biological structures is generally only about 2 nm.
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What are the two basic types of electron microscopes?
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the scanning electron microscope (SEM) and the transmission electron microscope (TEM)
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Describe how the SEM works and what it used for.
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it is useful for the study of the surface of a specimen. the electron beam scans the surface which usually coated with gold. the beam excites electrons on the surface and these secondary electrons are detected by a device that translates the pattern of electrons into a signal to a video screen. It has great depth of field which creates 3D like image.
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