Microscopes and Basic Measurement

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Microscopes and Basic Measurement

• How are they used to study the living environment?

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Measuring and Units

• Use a standardized system (metric system)
• Meters length
• Gram mass
• Liter volume

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Why Use Metric?

• Base 10 system
• Easier to convert units
• Simply multiply or divide by 10 to change unit

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Prefixes

• Used to show smaller or larger measurements
• Mega
• Kilo
• Hecto
• Deka
• Deci
• Centi
• Milli
• Micro
• Nano

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Important Unit for Microscopes

• Micrometers (microns) µm
• 1/1000th of a millimeter
• 1000 micrometers 1 mm

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How Big is a Micron?
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Early Microscopes

• Anton Van Leeuwenhoek (1670s)
• First to see and describe single celled organisms
  (protozoa)

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Robert Hooke (1665)

• Coined term cell

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Earliest Microscope?
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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.

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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

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Letting in Light

• 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

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• 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.

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Magnification

• How much can you enlarge the image?
• Ex 100x 100 times as big

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Finding Total Magnification

• 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

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Practice

• Find Total Magnification
• Ocular 2x, Objective 30x
• Ocular 10x, Objective 60x
• 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)

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Resolution

• How sharp can you get the image?
• Ability of microscope to distinguish two objects
  as being separate (ex one cell from another)

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What Happens to Image?

• Compound Microscopes
• Image becomes inverted and upside down

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What Happens to Image?

• When you increase magnification
• Object appears larger
• Field of view gets smaller

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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)

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Finding Field of View (F.O.V)

• Under Medium or High Power
• Need to set up a proportion
• Remember!!
• As magnification increases FOV decreases

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• Low power Magnification High power FOV
• High power Magnification Low power FOV
• Ex 100x HP FOV
• 500x 1500 micrometers
• 500x 150000
• HP FOV 300 micrometers

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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 es fit across FOV of 1800
  micrometers
• Each letter is about 600 micrometers

1800 micrometers 600 µm 3 letter e
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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

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• 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

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Other Equipment

• 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