Crawford's Microbiology Lab Practical #1

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Safety and Lab guidelines and Ch. 1-4
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1

A microscope with one lens

Simple Microscope

2

A microscope with 2 lens

Compount Microscope

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Ocular Lens

10x; Closest to eyes

4

What are the magnifications of the objective lenses?

10X, 40X and 100X

5

Which lens is used for oil immersion?

100X

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If you are using the 40X objective lens, what magnification are you using to view your specimen?

400X (10X of ocular Lens, times 40X of objective)

7

Diaphragm

Iris-like closure system below the stage which regulates the amount of light passing through the condenser

8

Resolving Power

ability to distinguish two points as distinct, separate objects rather than as one blurred image. Under oil immersion this distance between points should be 0.22 um. Resolving power depends on the wavelength of light (shorter=better), the design of the condenser, and use of immersion oil.

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Immersion Oil

prevents loss of light rays due to diffraction because the oil had the same refractive index as glass

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Total magnification

ocular magnification multiplied by the objective magnification.

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Parfocalism

one the specimen has been focused under low power, the microscope is parfocal if you are able to switch to higher magnification with a minimum of focal adjustment.

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Working Distance

distance between the bottom of the objective lens and the slide. As the magnification increases, the working distance decreases.

13

Light Intensity

Less light is required at low magnifications. As the magnification increases, the need for light increases. However, too much light can "burn out" the image.

14

Diameter of the Field

as the magnification increases, the diameter of the field decreases

15

Real Image

image passing into the objective lens from the specimen.

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Virtual Image

real image is further magnified by the ocular lens and passes to the retina of the eye. This is upside down the reversed right to left.

17

Course Adjustment Knop

used to bring specimen into approximate focus

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Fine Adjustment Knob

used to bring specimen into clear focus. When this knob is in mid-Range, white band is visible.

19

Bright field microscope

An instrument that magnifies an object by passing visible light directly through the lenses and object

20

Flourescence microscopy

An optical system on the light microscope that uses ultraviolet light to excite dye containing objects to flouresce.

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Phase contrast microscopy

An optical system on the light microscope that uses a special condenser and objective lenses to examine cell structure.

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Dark firld microscopy

An optical system on the light microscope that scatters light such that the specimen appears white on a black background.

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Opaque

not permitting light to pass through

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Translucent

some light passes through but not enough to permit visibility

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Opalescent

opal-like appearance; milky iridescence

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iridescent

exhibiting changing rainbow colors in reflected light

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Glistening

glossy

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2 examples of specimen that you would use oil for are.

Saccharomyas and Bacteria

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Phenol Red Broth

carbohydrate digestion