Transcript Microscopes and Basic Measurement

Microscopes and Basic
Measurement
How are they used to study the
living environment?
Measuring and Units
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Use a standardized system (metric system)
– Meters = length
– Gram = mass
– Liter = volume
Why Use Metric?
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Base 10 system
Easier to convert units
Simply multiply or divide by 10 to
change unit
Prefixes
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Used to show smaller or larger measurements
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Mega
Kilo
Hecto
Deka
Deci
Centi
Milli
Micro
Nano
Important Unit for
Microscopes
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Micrometers (microns) = µm
1/1000th of a millimeter
1000 micrometers = 1 mm
How Big is
a Micron?
Early Microscopes
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Anton Van Leeuwenhoek (1670’s)
First to see and describe single celled
organisms (protozoa)
Robert Hooke
(1665)
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Coined term “cell”
Earliest
Microscope?
Parts of a Compound
Microscope
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Contain two lenses that
cause light rays to bend
in such a way to produce
an enlarged image.
Lenses:
Ocular Lens: eyepiece lens
Objective Lens: can be low, medium or high
power
Look at magnification on lens
Lower power is smaller in size
Letting in
Light:
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Mirror or Illuminator:
directs light up through
the specimen
Diaphragm: regulates
amount of light
– Disk with different sized
“iris” or openings
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Arm: connects stage and
body tube
Stage: platform with
opening over which a
specimen is placed (clips to
hold slide)
Base: supports microscope
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Eyepiece (ocular): part you
look through, holds ocular lens,
magnifies 10x
Body tube: connects eyepiece
& objective lenses
Nosepiece: holds objective
lenses (can be turned)
Objective Lens: magnifies
image, can be low, medium,
high power
Focusing:
Coarse Adjustment Knob:
use on low power only!!
(never use with high power
you can break your slide!)
Fine Adjustment Knob:
once low power is focused
switch to high power and use
fine adjustment.
Magnification
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How much can you enlarge the image?
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Ex: 100x = 100 times as big
Finding Total
Magnification
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Multiply strengths of two lenses you
are using.
– Ocular lens x Objective lens
Ex:
Ocular = 10x
High Power Objective= 45x
Total Magnification = (10 x 45) = 450x
Practice
Find Total Magnification:
1. Ocular 2x, Objective 30x =
2. Ocular 10x, Objective 60x =
3. If Ocular is 10x and Total mag. = 350x
What is the strength of the objective
lens?
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Note:
As you increase magnification you
need to let in more light to see your
specimen (adjust diaphragm)
Resolution
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How sharp can you get the image?
Ability of microscope to distinguish two
objects as being separate (ex: one cell
from another)
What Happens to Image?
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Compound Microscopes:
– Image becomes inverted and upside
down
What Happens to Image?
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When you increase magnification
– Object appears larger
– Field of view gets smaller
Finding Field of View
(F.O.V)
Under Low Power: Use millimeter ruler
Ex: 1.5mm
Convert to micrometers
1 mm = 1000 micrometers
So 1.5 mm = 1,500 micrometers
(Move decimal over 3 to right)
Finding Field of View
(F.O.V)
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Under Medium or High Power
Need to set up a proportion
Remember!!
– As magnification increases FOV decreases
Low power Magnification = High power FOV
High power Magnification
Low power FOV
Ex:
100x
500x
=
HP FOV
1500 micrometers
500x = 150000
HP FOV = 300 micrometers
Determining the Size of
an Object Under a
Microscope
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View and draw object on low power
Estimate how many objects would fit
across diameter of field of view
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Divide the diameter of
FOV by the number of
objects that can fit
across it.
Ex:
– Three letter “e”s fit
across FOV of 1800
micrometers
– Each letter is about
600 micrometers
1800 micrometers = 600 µm
3 letter “e”
Comparing Microscopes
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Compound Light Microscope
Magnification 40x – 1500x
– 2-D image, inverted, upside down
– Uses stains to see details (may kill
specimen)
– Specimen must be thin to allow light
through
Dissecting Microscope:
Low mag. 10x – 20x
 See true image (right side up)
 Specimen can be alive
 Can use tools for dissecting specimen
 Binocular (two ocular lens) so you can see
3-D image
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Phase Contrast Microscope:
Uses special filters to show depth
without staining.
Can see interior details of living cells
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Electron Microscopes:
Much higher magnification and resolution
than microscopes that use light.
Magnifies up to 200,000x
Uses beam of electrons
Sample placed in vacuum
Cannot view living specimens
Allowed scientists to see structure of cellular
organelles
Other Equipment
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Centrifuge:
– Separates cell components by density
– Whirls test tubes at high speed
– Heaviest at bottom
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Micro-dissecting Tools
Used to dissect cells