Labs 1-4

Question 1

Compound Light Microscope

Answer 1

An instrument that uses light and multiple lenses to magnify objects/view specimens

Question 2

Magnification

Answer 2

The apparent increase in the size of an object

Question 3

Light Switch/Light Intensity Knob (Dimmer)

Answer 3

Turn the lamp on/off and control brightness; the higher the magnification, the more light is needed

Question 4

Ocular Lens

Answer 4

Magnify by 10X; pointer in the right lens; must be adjusted for your inter-eye distance

Question 5

Objective Lenses

Answer 5

4 lenses with increasing powers of magnification:

• Scanning Lens 4X
• Low Power Lens 10X
• High Power Lens 40X
• Oil Immersion Lens 100X

Question 6

Working Distance

Answer 6

The distance between an objective lens and the slide being viewed

Question 7

Total Magnification

Answer 7

Ocular power multiplied by objective power

- TM (using scanning lens) = 10 (ocular) X 4 (scan) = 40X magnification

Question 8

Condenser and Iris Diaphragm Lever

Answer 8

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

Question 9

Contrast

Answer 9

The difference in intensity between two objects or between an object and its background

Question 10

Mechanical Stage

Answer 10

Horizontal platform that supports the microscope slide

Question 11

Mechanical Stage Knobs

Answer 11

Move slide into correct position

Question 12

Stage Clips

Answer 12

Fasten slide to the stage

Question 13

Field of View

Answer 13

The area visible through the eyepiece

Question 14

Coarse Focus Adjustment

Answer 14

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

Question 15

Fine Focus Adjustment

Answer 15

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

Question 16

Nosepiece

Answer 16

Holds objective lenses and rotates them into position over the slide

Question 17

Parfocal

Answer 17

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

Question 18

Immersion Oil

Answer 18

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

Question 19

Resolution

Answer 19

The fineness of detail that can be examined using a scope

Question 20

Micrometer (um)

Answer 20

The unit used to measure field of view or the size of cells; 1/1000 of a millimeter

Question 21

Field of View Measurements

Answer 21

• Scan: 4.5 mm
• Low: 1.8 mm
• High .45 mm
• Oil Immersion: .18 mm

Question 22

Average Diameter of Cells

Answer 22

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

Question 23

Protozoans

Answer 23

Protists, single-celled, motile

Question 24

Flagellated Algae

Answer 24

Protists, single cells, green, motile

Question 25

Filamentous Algae

Answer 25

Protists, cells form chains, green, motile

Question 26

Nonfilamentous and Nonflagellated Algae

Answer 26

Protists, single cells, green, non-motile

Question 27

Invertebrates

Answer 27

Animals, large, multicellular, motile

Question 28

Aseptic Techniques

Answer 28

Procedures used to reduce the number (or kill) of microbes on a surface to prevent contamination; ex.: disinfection, flaming

Question 29

Negative Stain (Smear Stain)

Answer 29

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

Question 30

Negative Staining Procedure

Answer 30

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

Question 31

Spirochaetes

Answer 31

Very thin cells that do not stain well with positive stains

Question 32

Reasons for Conducting a Negative Stain

Answer 32

- 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