microscope_lab Flashcards
What are the low power objective lens called and their x
Scanning objective lens 4x, Low Power objective lens 10x
what are the correct order of steps to few a specimen at 40x
- click power switch to turn on light
- adjust light to appropriate brightness (contrast)
- focus at 4x using coarse focus knob
- Adjust ocular lenses to view one image
- focus using fine focus knob
- Adjust the stage to move the star to the center of microscope view
- Put 10x objective in place
- Focus using fine focus knob
- Put 40x objective in place
- Adjust using fine focus knob
when was the microscope invented
shortly before 1600 by zacharias janssen
The microscope was not used to examine microorganisms until___ when ______ examined scrapings of his teeth
1680, Antoni van Leeuwenhoek
Wha were early microscopes consisting of biconvex lenses, called
simple microscopes
whats a compound microscope
two lenses between the eye and the object, magnifies the object and illumination system (sun + mirror, or lamp) ensures enough light is available for viewing
_____ shows dark object in a bright field
bright field microscope
what does a stage do
holds the slide
microscope arm
for carrying the microscope
body tube
for transmitting the magnified image
stage clips
to hold the slide
above the light source is a ____
condensor
what’s a condenser
consists of several lenses that concentrate light on the slide by focusing it into a cone
iris diaphragm
the condenser has an iris diaphragm which controls the angle and size of the cone of light. AMOUNT of light
revolving nose piece
holds 3-4 objective lens
whats the magnification of the occular or eye piece
10-12.5x
if a microscope has only one ocular lens
monocular microscope
if a microscope has two ocular lenses
binocular microscope
coarse adjustment knob
is used for focusing with low power objectives (4x and 10x), moves stage longer distances
fine adjustment
is used for focuing with the high-power and immersion objective lenses
field of vision
area seen through a microscope
what are teh four objective lenses and their power
scanning lens (4x), low power lens (10x)
high power lens or high dry (40-45x), oil immersion lens (97 - 100x)
how to find total magnification of object
multiple ocular lens magnification by objective lens
the most important lens in microbiology is the
oil immersion lens
optical system could be built to magniy much more than 1000x magnification but the _____ would be poor
resolution
compound microscopes require a ___
light source
light may be reflected to the ______ by a ______ under the stage.
condensor, mirror
if your microscope has a mirror the ____ or a ____ can be used as a light source
sun or a lamp
most compound microscopes have a built in_____ at the base for a light source.
illuminator (not usually used with mirror)
the ______ of the light of an illuminator can be adjusted with a wheel that regulates the amount of current to the bulb
intensity
intensit yof the light can be adjusted with a wheel that regulates the amount of _____ to the bulb
current
higher magnification requires (more/less) which can be obtained by adjusting the _____
more, iris diaphragm
another word for resolution
resolving power
what is resolution or resolving power
the ability of a lens to reveal fine detail or two points distinctly sperated
resolving power is expressed in units of
length
the _____ the distance the better the resolving power
smaller
what is the equation of resolving power?
RP = wavelength of light used / 2x numerical aperture
smaller wavelengths of light ____ resolving power
improve resolving power
This is an example of :
as seen in electron microscopes, electrons have an extremely short weave length adn result in excellent resolving power
smaller wavelengths of light improve resolving power
high numerical aperture _____ resolving power
improve
electron microscope has a resolving power of
less than .2nm
light microscope has a resolving power of about
200 nm
where to find numerical aperture
engraved on the side of each objective lens
what does numerical aperture depend on
depends on the maximum angle of the light entering the objective lens and on the refractive index (the amount the light bends) of the material (usually air) between the objective lens and the slide,
whats refractive index
amount the light bends
numerical aperture is abreviated ___
N.A.
equation of N.A.
N.A. = N sin θ, where
N = refractive index of medium
θ = angle between the most divergent light ray gathered by the lens and the center of the lens
why is light refracted when it emerges from the slide
because of the change in medium as the light passes from glass to air
when immersion oil is placed between teh slide adn the oil immersion lens, the light ray continues without refraction because :
immersion oil has the same refractive index ( N = 1.52) as glass. when you look through immersion oil you can not see the glass rod inside
the identical N values of the glass and immersion oil ____ light loss
minimizes
as light rays pass through a lens they are bent to converge at the _____ where an image is formed.
focal point
what is spherical aberration
when you bring the center of a microscope field into focus teh periphery may be fuzzy because of the curvature of the lens, resulting in multiple focus points.
how to limit spherical aberration
minimized by using the iris diaphragm, which eliminates light rays to the periphery of the lens or using multiple lenses that result in a flat optical system
whats chromatic aberration ?
caused by the prism like effect of the lens as various wavelengths of white light pass though to a different focal point for each wavelenngth.
how to minimize chromatic aberrations
using filters (usually blue)
by a lens systems corrected for red and blue light (achromatic lens)
lens corrected for red, blue and other wavelengths (apochromatic lenses)
use a light source of one wavelength(monochromatic light) most expensive.
always focus by moving the lens ___ from the slide
away
carry the microscope with ___ hands, one hand _____ the base and one hand on the ____
both hands, one hand beneath the base and one hand on the arm
when using the low powered lens keep the ______ barley open
iris diaphragm - to achieve good focus
t/f use only lens paper to clean lenses and wet if needed with opital lens cleaner
true
t/fmake sure condensor is right below slide, may need to move up
true
micrometer = how many meters
1 um = 1/1 millionth of a meter
whats parfocal
when a subject is in focus with on lens it will be in focus with all of the lenses,
whats working distance
distance between the objective lens and the specimen
t/f working distance increases as magnification increases
false decreases.
