02 Dissecting Microscope. A B Carrying a Microscope.
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Transcript of 02 Dissecting Microscope. A B Carrying a Microscope.
02
Dissecting Microscope
A B
Carrying a Microscope
• Return the lowest power objective in place
• Wrap the cord around the base
• Return dustcover
Storing The Microscope
• Use lens paper on all glass parts of the microscope.
Cleaning the Microscope
Dissecting Microscope & Parts
Free standing illuminator
Pond Water Sample
Paramecium
Euglenia
Volvox
Clamydomonas
SpirogyraRotifer Daphnia
Prepare wet mount for dissecting scope• Pond water
Look at specimen under high power and draw what you see.
Use proper clean-up technique
Activity
Phase Contrast Microscope
Muscle tissue Downy mildew of grape
• Imperfections in glass• Peaks and troughs
don’t line up• These waves are in
different phases• PCM used to transform
phase differences into intensity differences, thus increasing contrast
Understanding Phase Contrast Microscopy
light
glass
light
waves
Destructive interference(Dark phase)
Constructive interference (Light phase)
Understanding Phase Contrast Microscopy
Dark FieldBright Field
Phase contrast
Comparison of Light Microscopy
Course adjustment knob
Fine adjustment knob
Y-axis knob
X-axis knob
Specimen holder
ocular
objective
Light intensity lever
Light intensity preset button
stage
Revolving nose piece
Aperture iris diaphragm ring condenser
• Use lens paper on all glass parts of the microscope.
• Clean oil immersion lens with chemicals provided by your instructor
Cleaning the Microscope
Using the microscope
• Always observe using the LOWEST POWER objective first.
• Focus using the COARSE ADJUSTMENT KNOB to bring the object into focus. Bring the object into sharp focus by using the fine adjustment knob.
• Focus, and then move to a higher power objective, if needed.
• Use only the FINE ADJUSTMENT KNOB when using the HIGHEST (longest) POWER OBJECTIVE.
• Keep both eyes open to reduce eyestrain. • Determine total magnification of the object by
multiplying the power of the ocular (10x) the power by the power of the objective.
Preparing a slide
• Using a pipet or dropper, add a drop of water or another solvent to a clean microscope slide. Then, place the specimen in the water.
• Place the edge of a coverslip on the slide so that it touches the edge of the water.
• Slowly lower the coverslip to prevent the formation of air bubbles.
The effects of immersion oil on resolution
40x 100x
Oil Immersion Lens
base
ocular
objective
Illumination intensity
stage
Nose piece
Specimen holder
Course adjustment
X-axis knob
Condenser
Iris diaphragm(aperture diaphragm ring)
Fine adjustment
y-axis knob
For Light Microscope use set to 0
Animal Cell
Plant Cell
Prepare wet mount• Cheek cell• Elodea cell• Onion cell• Bacterial cells in yogurt
Look at specimen under high power and draw what you see.
Use proper clean-up technique
Activity
Cheek Cell
Elodea
Epidermal Onion Cell
Dispose Biological material
Dispose Sharps
Clean Up
Microscope Parts Quiz
Microscope Quiz
1.
1. Which objective uses oil?2. If your ocular is 10x and your
objective is 40x what is the total magnification of your image?
3. Why do you need a cover slip and how do you avoid an air bubble?
4. What is the difference between a light microscope and a dissecting microscope?
• When looking through the ocular you will see 2 rings
• The may or may not be concentric.• By turning the centering adjustment
screws o the condenser, you align the rings so they become concentric
Aligning rings
• Brightfield –absorptionLight is transmitted through the sample. Only useful
for specimens that can be contrasted via dyes. Very little contrast in unstained specimens.
• Darkfield -scatteringThe illuminating rays of light are directed from the
side so that only scattered light enters the microscope lenses, consequently the cell appears as an illuminated object against the view.
• Phase Contrast- phase interferenceIncident light [Io] is out of phase with transmitted
light [I] and when the phases of the light are synchronized by an interference lens, a new image with greater contrast is seen
Dark-Field Microscopy• Modified condenser
contains disc in center• Only light refracted by
specimen can enter objective.
• Objects surrounded by halo.
• Advantage can see smaller objects like spirochetes, internal structures highlighted.
• Disadvantage objects look bigger than they actually are.
Phase Contrast Microscopy
• Light passes through annular diaphram.
• Causes light waves to become “in phase” or synchronized.
• Advantage can highlight internal cell structures and details.
• Disadvantage - none.