Labs 1-4 Flashcards
Compound Light Microscope
An instrument that uses light and multiple lenses to magnify objects/view specimens
Magnification
The apparent increase in the size of an object
Light Switch/Light Intensity Knob (Dimmer)
Turn the lamp on/off and control brightness; the higher the magnification, the more light is needed
Ocular Lens
Magnify by 10X; pointer in the right lens; must be adjusted for your inter-eye distance
Objective Lenses
4 lenses with increasing powers of magnification:
- Scanning Lens 4X
- Low Power Lens 10X
- High Power Lens 40X
- Oil Immersion Lens 100X
Working Distance
The distance between an objective lens and the slide being viewed
Total Magnification
Ocular power multiplied by objective power
- TM (using scanning lens) = 10 (ocular) X 4 (scan) = 40X magnification
Condenser and Iris Diaphragm Lever
Controls the amount of contrast that the microscopic specimen has; moved right - field of view gets darker/more contrast; moved left - field of view gets brighter and clear cells become more difficult to see, but colors (stains) are brighter
Contrast
The difference in intensity between two objects or between an object and its background
Mechanical Stage
Horizontal platform that supports the microscope slide
Mechanical Stage Knobs
Move slide into correct position
Stage Clips
Fasten slide to the stage
Field of View
The area visible through the eyepiece
Coarse Focus Adjustment
Moves the stage up and down quickly; changes working distance and brings slide into focus; should only be used when using scanning power objective lens
Fine Focus Adjustment
Moves the stage up and down slowly; changes working distance and brings slide into focus; should be used to focus the specimen on low, high, and oil immersion
Nosepiece
Holds objective lenses and rotates them into position over the slide
Parfocal
An image will remain in focus when changing from a lower-power objective lens to a higher-power objective lens, with little focusing necessary with the fine focus adjustment
Immersion Oil
Decreases light refractivity entering the specimen; at high magnifications, light refractivity leads to poor resolution and blurry images; only a single drop is necessary on the area being examined
Resolution
The fineness of detail that can be examined using a scope
Micrometer (um)
The unit used to measure field of view or the size of cells; 1/1000 of a millimeter
Field of View Measurements
- Scan: 4.5 mm
- Low: 1.8 mm
- High .45 mm
- Oil Immersion: .18 mm
Average Diameter of Cells
Field of view divided by the number of cells across the field of view; to convert to um, multiply by 1000 or move the decimal point three places to the right
Protozoans
Protists, single-celled, motile
Flagellated Algae
Protists, single cells, green, motile
Filamentous Algae
Protists, cells form chains, green, motile
Nonfilamentous and Nonflagellated Algae
Protists, single cells, green, non-motile
Invertebrates
Animals, large, multicellular, motile
Aseptic Techniques
Procedures used to reduce the number (or kill) of microbes on a surface to prevent contamination; ex.: disinfection, flaming
Negative Stain (Smear Stain)
Useful procedure for studying the morphology of bacterial cells and characterizing some of the external structures that are associated with them; cells appear as transparent objects against a dark background
Negative Staining Procedure
Consists of mixing the organism with a small amount of stain (india ink or nigrosin) and spreading a very thin film over the surface of the microscope slide
Spirochaetes
Very thin cells that do not stain well with positive stains
Reasons for Conducting a Negative Stain
- Quick
- Determine morphology (shape and size)
- To view external features
- No heat fixation: no cell shrinkage or distortion and determination of size is more accurate
- Possible to view spirochaetes
