Micro Ch.4,5,6 Flashcards
light
affects our ability to visualize objects with the human eye
wavelength
*length of a light ray
*represented by Greek letter lamda
*equal distance between two adjacent crests or two adjacent troughs of a wave
resolution
*ability to see two items as separate and distinct units rather than one fuzzy overlapping image
*light must pass between objects to be seen as separate
*key: get light of short enough wavelength to fit between objects.
reflection
*light strikes an object and bounces back- reflection has occurred.
transmission
*the passage of light through an object
*most microorganisms will make use of transmitted light
absorption
*light rays neither bounce off nor pass through an object
*light rays are taken up by an object- absorption has occurred
iluminescence
*absorbed light rays are changed into longer wavelengths and reemitted
refraction
*bending of light as it passes from one medium to another of differing density
*gives rise to an angle of refraction or the degree of bend
index of refraction
*measures the speed at which light passes through a material
*substances that have different indices of refraction, light will bend as it passes from material to material
*can cause loss of light and blur an image
immersion oil
*oil joins the slide and lens together
*prevents refraction of the image
staining
*increases differences in indices of refraction
*makes it easier to observe detail
light microscope
*any microscope that uses visible light to make specimens observable
compound microscope
*a microscope with more than one lens
*gives distortion free image
monocular vs binocular lens
*monocular- single eyepiece
*binocular- two eyepieces
blue filter
*filters out long wavelengths of light, leaving shorter wavelengths and improves resolution
condenser
*converges the light beam so that it they pass through the specimen
iris diaphragm
controls amount of light that passes through the specimen to the objective lens
objective lens & total magnification
*magnifies the image before it passes through the body to ocular lens
* Scan- (4X) x (10X) = 40X total mag.
*Low power- (10X) x (10X) = 100X total mag.
*High-dry power- (40X) x (10X) = 400X total mag.
*Oil immersion- (100X) x (10X) = 1000X total mag.
mechanical stage
allows precise control of moving the slide
focus adjustment knobs
*coarse adjustment- changes distance between objective lens and specimen rapidly
*fine adjustment- changes the distance between the objective lens and specimen slowly
dark field microscopy
*microscope adapted for dark-field illumination have condenser that causes light to reflect off the specimen at an angle
*a light object is seen on a dark background
phase-contrast microscopy
*used to observe live specimen
*light is slowed down and diffracts the change in light speed, seen as different degrees of brightness
*short depth of field, can produce a nearly 3-D image.
fluorescent microscopy
*ultraviolet light used to excite molecules, so they release light of longer wavelengths
*produces a brilliant shade of orange, yellow, yellow green
digital microscopy
*they have auto-focus, auto-aperture, auto-light, motorized stage and magnification changers
*just plug in and power on
*magnification is limited on digital microscopes
electron microscopy
*allows small structures (less than 0.2 micrometers) to be visualized
*uses a beam of electrons and an electromagnet to focus the beam
*can resolve objects close to 20 nano meters (nm), magnifying at 50,000X total magnification
degree of contrast
the contrast between structures being observed and their background
wet mount
drop of medium containing the organism is placed on a microscope slide, can be used to view live organisms
smear
*organism is thinned out and smeared across a slide, then heat fixed
heat fixed
*kills the organism
*organism adheres to the slide
*alters the organism so that they readily accept the stain