Chapter 4: Microscopy

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45 Terms

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Astigmatism
a.k.a. spherical aberration -- results from a lens not being properly spherical.
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Infinity Corrected Lens
Produce very high- quality images and allow for the addition of a variety of analytical components to the microscope.
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Birefringence
The result of this division of light into at least two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, depending on the polarization of the light.
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Numerical Aperture
An angular measure of the lenss light- gathering ability and, ultimately, its resolving quality.
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SEMs
________ are used in forensic laboratories to analyze a wide variety of samples, including paint, particles, fractures, toolmarks, and gunshot residue.
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Objective Lens
The most important part of the microscope.
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BSEDs
________ assist analysts in detecting materials of interest, like gunshot residue particles.
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Apochromats
Contain several internal lenses that have different thicknesses and curvatures in a specific configuration unique to ________.
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Lens
A translucent material that bends light in a known and predictable manner.
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Analyzer
Located above the objectives, it can be manually slid into or out of the light path.

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It is a device used to determine whether the light is plane polarized or not.
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Auguste Michel Lévy
a French geologist, was born in Paris and became inspector-general of mines and director of the Geological Survey of France.
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Compound microscope
Employs a magnification system that exceeds the limits imposed by simple lenses.
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Critical Illumination
Concentrates the light on the specimen with the condenser lens; this produces an intense lighting that highlights edges but may be uneven.
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Regular achromats
________ lack correction for flatness of field, but recently most manufacturers have started offering flat- field corrections for achromat objectives, called plan achromats.
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microscope stage
The ________ is the platform where the specimen sits during viewing.
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simple lens
A ________ focuses a flat specimen on a microscope slide onto the lens, a rounded surface.
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transmission electron microscope
In ________, the electron beam passes through a specimen that has been very thinly sectioned and projects the beam onto a specially treated plate that transmits the image to a monitor.
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Refractive Index
The relative speed at which light moves through a material with respect to its speed in a vacuum.
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Wavelength dispersive spectrometer
Measures the wavelength of the emitted radiation using a tightly spaced crystal lattice.
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Focal Length
The distance between the two points of focus on either side of the lens.
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Simple magnification system
a single lens used to form an enlarged image of an object
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Compound magnification system
Where magnification occurs in two stages and the total magnification is the product of the magnification of the first lens and the second lens
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Tube length
The distance from the lowest part of the objective to the upper edge of the eyepiece.
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Condenser
Used to obtain a bright, even field of view and improve image resolution
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Field diaphragm
A control that allows more or less light into the lens system of the microscope
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Köhler illumination
Sets the light rays parallel throughout the lens system, allowing them to evenly illuminate the specimen
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Polarizing light microscope
Exploits optical properties of materials to discover details about the structure and composition of materials, and these lead to its identification and characterization
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Isotropic Materials
Demonstrate the same optical properties in all directions, such as gases, liquids, and certain glasses and crystals
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Interference Colors
The wavelengths being added and subtracted through interference; these colors are caused by the interference of the two rays of light split by the anisotropic material interfering destructively with each other
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Michel-Levy Chart
a chart of diameter, birefringence, and retardation
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Back-scattered electron detector
Detects elastically scattered electrons.
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Energy-dispersive spectrometer
A used technique for elemental analysis and chemical composition determination, associated with electron microscopy.
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Virtual Image
The observer looks at the first image with a lens that produces an enlarged image called a _______.
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Real image
the one that could be seen on the screen—that is, projected onto the screen.
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Lens
a translucent material that bends light in a known and predictable manner.
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Eyepiece / ocular
the lens that the observer looks into when viewing an object microscopically.
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Chromatic Aberration
where white light from the specimen is broken out into multiple colored images at various distances from the lens.
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curvature of the field
a rounded surface wherein a simple lens focuses a flat specimen on a microscope slide onto the lens.
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plain achromats
Regular achromats lack correction for flatness of field, but recently most manufacturers have started offering flat-field corrections for achromat objectives, called _____.
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Refraction
occurs as light passes from one medium to another when there is a difference in the index of refraction between the two materials, and it is responsible for a variety of familiar phenomena such as the apparent distortion of objects partially submerged in water.
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Polarizing light microscope
exploits optical properties of materials to discover details about the structure and composition of materials, and these lead to its identification and characterization.
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Polarizer
a special filter used when the light passes through it, the only light that passes is that which vibrates in that “preferred” direction.
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Phosphorescence
Long-lived emission.
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Fluroscence
This is where the emission stops when the excitations stops.
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Electron microscopy
______ employs a particle beam of electrons focused on magnetic lenses. It does have a much higher resolving power and greater depth of field than light microscopes and can magnify a specimen hundred of thousands of times.