Topic: Microscope
MI: Explain the function of microscopes.
Do Now: What do we use to observe cells more closely?
HW: study for Wednesday’s test
Microscope • Instrument that
produces a larger
image of an object
(specimen) using
lenses
Lens
• Piece of curved glass
• Causes light rays to
come together or spread
apart as they pass
through
• Magnify an image
Simple
Microscope
• Uses 1 lens and
light to magnify
the specimen
Compound
• Uses 2 lenses &
Light
light to magnify
Microscope specimen
• Need stain (dye)
to see it
Blood
Cheek Cells 40x
Onion Cells 10x
Phase
• View living specimens
without staining
Contrast
Microscope
Cheeks cells as they would appear without iodine with a
compound microscope.
Same image with phase contrast objectives. White dots
inside each cell are the nuclei.
Light microscope
Phase contrast
microscope
Human lymphocyte (phase-contrast
microphotograph).
Phase contrast light micrograph of
Paramecium highlighting the two contractile
vacuoles including the radial arms each
composed of ampulla and collecting canal.
• Electron microscope: illuminates
the specimen and can magnify
image up to 100,000x
– Uses beam of ELECTRONS instead
of light
Fly
Spider
Termite head
Tapeworm
Blood
Pollen Grains
Scanning electron microscope image of a leaf from a Black Walnut tree. Image
shows a cross-section of a cut leaf, its upper epidermal layer, mesophyll
layer with palisade cells and vascular bundles, and lower epidermal layer.
The protrusion at center is just over 50 microns tall. (Dartmouth Electron
Microscope Facility/Dartmouth College)#
Hair
PARTS OF A MICROSCOPE
eyepiece • Ocular lens (usually 10x)
• Lens you look through
1
Objective• Contains lenses
lenses
• Low, medium, high power
Low Power
High Power
A
Low Power
B
High Power
Larger Field of view Smaller Field of View
• Low power objective = used to
locate the specimen on the
slide
– Larger field of view (See more
of the slide)
• High power objective =
– More magnification
– Smaller field of view
Nosepiece
• Holds & rotates obj.
lenses
Body Tube • Connects eyepiece
to nosepiece
Arm • Supports body tube
Base • Bottom = support
Stage • Where slide is placed
Stage
Clips
• Hold slide in place
Mirror/
light
• Illuminates specimen,
provides light
Diaphragm • Controls the
AMOUNT of light
used
10/23/08
Aim: How do we use a microscope?
Do Now: DON’T COPY THE QUESTIONS!!!!
1. Which objective gives you a larger field of
view?
2. Which structure is used to adjust the amount of
light reaching the specimen?
3. If your searching for a cell on your slide, which
objective should you use?
HW: Ditto – Parts of a Compound Microscope
Coarse
• Larger focusing knob
Adjustment
Knob
• For focusing under LOW
POWER ONLY
• If used under high power,
the objective lens
and/or slide can break
Fine
Adjustment
Knob
• Sharpens image
• Focusing for High
Power
Review: Identify the structure being
described.
1. Used to focus the specimen under high
power.
2. Adjusts the amount of light reaching the
specimen.
3. Objective used to view a larger field of
view needed to search for a specimen.
4. Used to focus specimen under low
power.
5. Contains lenses.
MI: How do we use a
microscope?
Total
magnification
• Eyepiece lens
magnification
x
objective lens
magnification
Total magnification=4 x10= 40
100x
400x
Rules
when
using a
microscope
1. Carrying microscope =
one hand on arm, other
hand under base close to
your body
10/24/08
Aim: Using the Microscope
Do Now: Give the total magnification for the
following –
1. Ocular is 10x and objective used is 35x
2. Ocular is 10x and the objective used is 5x
HW: Bring in your signed progress report and
continue researching and working on your
science fair project.
2. DO NOT use the coarse
adjustment under high power
bc it can break the lens or the
slide
3. Always start off with low
power bc it gives you a greater
field of view.
LOW
HIGH
4. Before switching to
high power you must:
- focus your image
- center your image
5. When switching from
low to high power, amount
of light decreases. Make
sure you adjust the
diaphragm.
6. When cleaning a lens, use
LENS PAPER.
–Do not use a napkin, or paper
towel…
Staining • Make cell parts
more visible
Unstained
cheek cells
Stained
cheek cells
• Examples:
1. Lugol’s Iodine (plant
cells)
Onion Cells stained with Lugol’s Iodine
2. Methylene blue
(animal cells)
Cheek Cells
Unstained
Stained
Skin Cells stained with Methylene Blue
Wet 1. Place a drop of
water on the slide
mount
2. Place object on the
slide.
3. Slowly lower the cover slip
onto specimen on an angle to
avoid AIR BUBBLES.
4. Excess water should be
absorbed with a paper towel.
How do • Upside down &
backwards
images
appear?
On the slide Seen through lens
F
10/27/08
Aim: Using the Compound Microscope
Do Now:
1. Which objective gives a smaller field of
view – low or high power?
2. Which field of view is usually darker – high
or low power? What structure would you
use to adjust the amount of light?
HW: Finish labeling the microscope picture on
the lab.
What
happens
when
you
move
the
slide?
• Image moves in
opposite direction
Review:
1. Explain one rule that must be followed
when using the microscope.
2. What do we use to make cell parts more
visible?
3. Which way will a cell appear to move
when moving the microscope to the left
and down?
4. What happens to the image of the
specimen when viewed with a
microscope?