Crawford's Microbiology Lab Practical #1
A microscope with one lens
A microscope with 2 lens
10x; Closest to eyes
What are the magnifications of the objective lenses?
10X, 40X and 100X
Which lens is used for oil immersion?
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)
Iris-like closure system below the stage which regulates the amount of light passing through the condenser
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.
prevents loss of light rays due to diffraction because the oil had the same refractive index as glass
ocular magnification multiplied by the objective magnification.
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.
distance between the bottom of the objective lens and the slide. As the magnification increases, the working distance decreases.
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.
Diameter of the Field
as the magnification increases, the diameter of the field decreases
image passing into the objective lens from the specimen.
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.
Course Adjustment Knop
used to bring specimen into approximate focus
Fine Adjustment Knob
used to bring specimen into clear focus. When this knob is in mid-Range, white band is visible.
Bright field microscope
An instrument that magnifies an object by passing visible light directly through the lenses and object
An optical system on the light microscope that uses ultraviolet light to excite dye containing objects to flouresce.
Phase contrast microscopy
An optical system on the light microscope that uses a special condenser and objective lenses to examine cell structure.
Dark firld microscopy
An optical system on the light microscope that scatters light such that the specimen appears white on a black background.
not permitting light to pass through
some light passes through but not enough to permit visibility
opal-like appearance; milky iridescence
exhibiting changing rainbow colors in reflected light
2 examples of specimen that you would use oil for are.
Saccharomyas and Bacteria
Phenol Red Broth