microscopy and cell structure Flashcards
(52 cards)
what are light microscopes
light rays focused and magnified by lenses
what are compound light microscopes
2 sets of lenses- ocular and objective
used to study small and thinly sliced objects
total magnifications of 40x to 1000x on our scopes
what are stereomicroscopes for
“dissecting microscope” to study small but visible objects
total magnifications about 10x
what are ocular lenses
-the lenses you look through usually
-10x magnification distance between -eyepieces can be adjusted
-can slide up and out of the scope but never remove them
what are objective lenses
-set of 4 lenses mounted on a turret which can be rotated to bring any one of the objectives into position
-mag. of each objective is printed on it but never use 100x objective
what is the stage
-horizontal surface where slides are placed to be viewed
-can be moved left-right and toward the viewer or away using the stage control
light source = illuminator
usually has an on/off switch and control for brightness
what is the condenser
-lens system below the stage that focuses light from the illuminator up through the hole in the stage and through the slide
-focus can be adjusted with a ring or lever
what is the diaphragm
-opening size can be changed affecting the light from the illuminator
-usually use smallest opening that illuminates
how to focus the microscope
adjusting the height of the stage where the slide rests through the course adjustment or the fine focus adjustment
coarse focus adjustment
-knob that moved the STAGE up or down by LARGE amount per rotation
-same vertical distance per rotation regardless of which objective is in place*
-use only with the 4x and 10x objectives
fine adjustment
-knob moves the stage up or down by a SMALL amount per rotation
-same vertical distance regardless of objective
-use only with the 40x objective
can does improper use of the focusing knows do
drive the objective lens through the slide being viewed and breaking it
What is the compound light microscope used for
to view and study biological objects that cannot be seen with the naked eye
what is the magnification
property of a microscope that enlarged the image
what is the total magnification formula
ocular mag X objective mag
what is the resolving power (resolution)
the ability of a lens system to distinguish 2 points that are close together
What can resolving power be thought of as
a function of the quality of the lenses
what factors is the resolving power of a microscope lens limited by
-quality of lens (NA) numerical aperture
-wavelength of light
does better resolving point correspond to a smaller or larger number
smaller
how is resolving power improved
by using shorter wavelength light and lenses of a higher optical quality
what is contrast
the difference in light intensity between the image and the background relative to the overall background intensity
what are used to enhance contrast
strains
how do strains enhance contrast
by coloring (staining) a specimen so that the light coming through it will appear more distinct
