Lab 1 Flashcards
Ocular Lenses
located inside eyepiece, magnifies specimen
Objective lenses
Series of lenses located on nosepiece, magnifies specimen
Arm
Used for hand grip when carrying
Coarse Focus Knob
Roughly focuses specimen by changing distance between objective lens and specimen
Light Source
Emits light onto specimen
Blue Filter
Increases Resolution by reducing light wavelength
Mechanical Stage
large, flat surface that supports slide/specimen over the hole that admits light from below, allows for movement of the slide using mechanical stage knobs
Mechanical Stage Knobs
moves slide around stage
Fine Focus Knob
Sharply focuses specimen by changing distance between objective lens and specimen very precisely
Condenser
Contains 2 lenses that focus light on specimen
Iris Diaphragm
regulates amt of light passing through lenses in the condenser, increases visibility of semi-transparent objects
Iris Diaphragm Lever
opens and closes iris diaphragm
Condenser Adjustment Knob
Moves Condenser up and down
Lamp Switch
turns light on or off
lamp intensity dial
adjusts brightness produced by light source
stage
large flat surface supporting slide over hole that admits light from below
main switch
controls supply of power to microscope, must be on for either light to work
T switch
turns light BELOW specimen on or off
I switch
turns light ABOVE specimen on or off
Stage Clips
holds a slide in position over stage
unaided eye resolution is
0.1mm in length
max magnification of compound light microscopes
2,500x
max resolution of compound light microscopes
0.2micrometers, 0.4micrometers without immersion oil
what are properties of image produced by compound light microscopes?
images are inverted and reversed
what are properties of image produced by dissecting light microscopes?
images are right side up
magnification
enlargement of an image
depth of field
vertical distance that remains in focus at each magnification
resolution
clarity and sharpness of an image, minimum distance that 2 points can be separate and still distinguished as 2 units
what is resolution affected by?
wavelength of light because the longer the wavelength, the more the diffraction, resulting in blurry image whereas the shorter the wavelength, the less the diffraction resulting in sharper image
how do you improve resolution?
- using blue filter to reduce wavelength of light that enters condenser
- using immersion oil that decreases diffraction, increasing chances of light waves entering objective lens
contrast
quality that makes image stand out better, the ability to discern detail
how do you improve contrast?
- stain layers between tissues and cells of thin sectioned specimen using artificial dyes
- use speical light microscopes that use diff types of light to make image clearer or easier to see
- reduce amount of light using either iris diaphragm or light intensity dial or adjusting condenser
What is the relationship between magnification and depth of field?
the higher the magnification, the smaller the depth of field
Why must a microscope increase magnification AND resolution?
high magnification is NOT valuable without good resolution
How do electron microscopes produce images?
Uses electron beams with very short wavelengths
What is resolution of Electron Microscopes?
0.2nanometers or 0.0002micrometers
What is process of using Transmission Electron Microscopes?
Specimen undergoes dehydration process, embedded in resin that solidifies
Sliced thinly with a microtome
Slices are put onto small copper grid and stained before being placed into the TEM in a vacuum
Specimen and grid are mounted inside objective lens
Electron beam passes through specimen, and electromagnets are used as lenses to focus and magnify image
As electrons pass through sample, they are deflected from stained portions and transmitted through unstained areas
Electron microscopes can view specimens 50-100µm thick
What is process of using Scanning Electron Microscopes?
Specimen is put on small copper grid and coated with thin layer of gold/platinum and put in the SEM in a vacuum
A beam of electrons bombard specimen surface and scams back and forth across it, produces image w/ 3D detail and great external detail
Electrons do NOT pass through specimen
Depth of field greater than that if any other microscope
How do you calculate actual size of specimen?
Actual Size(mm) = fraction of field occupied x field diameter(mm)
How do you calculate speed of specimen?
Speed of specimen (mm/s) = distance 9mm) ÷ time (s)
How do you calculate magnification?
Magnification = size of image (mm) ÷ actual size (mm)
How do you convert between milimeters, micrometers, and nanometers?
1cm = 10mm
1mm = 1000µm
1µm = 1000nm
parfocal
an object in focus at low power should be relatively focused when you switch to higher powers, small adjustment on fine focus is all that is necessary
Why do you not move stage down before switching objective lenses?
you will go out of focus
Why do you pick up coverslips by the edges?
so you won’t smudge it or get fingerprints on it
field diameter of low power objective lens
4.5mm
field diameter of medium power objective lens
1.8mm
field diameter of high power objective lens
0.4mm
Which kind of microscope can you view live specimens?
light microscopes, electron microscope specimens are dead
Which microscope produces 3D images?
Dissecting Light microscope and Scanning electron microscope, transmission electron microscope and compound light microscope produces 2D images
Which kind of microscopes can you use to see external structures and entire specimens?
Scanning Electron Microscopes and Dissecting Microscopes, Transmission Electron and Compound Microscopes are used to view internal, sectioned specimens
What is maximum magnification of electron microscopes?
300,000x
When should you never use the coarse focus knob when using compound light microscopes?
When using the medium and high power objective lenses, you might smash lenses into the slide and because you might lose focus of the specimen by roughly focusing specimen
