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Microscopes
The Discovery of Cells
Quiz
Number paper from 1-5
Identify the following pictures
Question 1
Question 1: Bacteria
Question 2
Question 2: DNA
Question 3
Question 3: Breast Cancer Cell
Question 4
Question 4: Alga- red tides
Question 5
Question 5: Bed bug
Learning Targets
1. Describe how a microscope works.
2. Calculate the total magnification of an image.
3. Compare the different types of microscopes.
Why? To see microscopic world
How does a microscope work?
Magnificationenlargement of an objectcompare size of image to actual size of
object
total magnificationocular power x objective power = total
magnification
Microscopes
MicroscopesResolution – capacity to show 2 points that are close together as separate
. . .
10x 1000x
Poor Resolution = Blurry ImageGood Resolution = Clear Image
Resolution
How does a microscope work?
Parfocalboth low and high power objectives are
adjusted to the same focuseasily switch between both objectives
What happens as magnification increases?
1. field of view decreases
2. brightness decreases
3. resolving power increases
Staining
Coloring cell structure
With dyes to reflect light
Certain cell parts absorb certain stains
Kills cells or disturbs contents Vital stains-dyes that highlight structures
in living cells
What are the different types of microscopes?
Compound light microscope
Stereoscopic dissecting microscope
Electron microscope
Compound Light Microscope
Compound Light Microscope
has 2 or more lenses (eyepiece and objective)uses transmitted light (light passes through object)must use thin specimen so light can pass thrucan use live specimensusually doesn’t exceed total mag. of 2000xOur scopes in class are capable of 400xonly see specimen in 2D
Compound Microscope Images
Human Hair (x 400)
Mite
Paramecium
Compound Light Microscope
Structures & Functions
Compound Light Microscope
Eyepiece/Ocular – The lens through which the scientist looks
Body Tube – Connects eyepiece to microscope
Revolving Nosepiece – Holds 3-4 objectives (magnifying lens), turns for objective selection.
Compound Light Microscope
Scanning Objective - Used for locating objects & scanning the slide quickly (Red Line- 4X)
Lowest power objective
Low Power Objective – Lens that allows you to find & center the object on a slide. Yellow line around the objective (10x)
High Power Objective - Lens that zooms in for closer viewing (40X)
Blue line around high power
Compound Light MicroscopeStage – platform upon which the slide rests
Mechanical Stage – movable clips that hold & move the slide
Iris Diaphragm – transparent lens through which light travels. Size and brightness can be adjusted.
Lamp – light source needed for viewing the specimen
Stereoscopic Dissecting Microscope
uses reflected light to produce image
range of magnification 10x-60x
Images from a Stereoscope
Penny – Abe’s face
Penny – back
Beetle
Stereo Dissecting Microscope
2 eyepieces to produce 3-D image
Uses reflected light to illuminate surface of specimen
Used on large objects which light cannot pass through
Magnifies object 5x – 60x
Electron Microscope
2 TypesScanning electron microscope (SEM)Transmission electron microscope (TEM)
Electron MicroscopeDiscovered in Germany in 1930’s and 1940’s
Uses beam of electrons to see image NOT light
Image is produced on a T.V. monitor in black & white (no light)
Much higher resolution
Limitations Can’t view living things due to vacuum in interior Very expensive Very big, must have own foundation
Transmission electron microscope (TEM)
Electrons go through very thin slice of specimen – detailed image on T.V. screen
200,000x (can be increased to 1,000,000x)
Images from a TEM
Bacteria
E.coli bacteria dividing
Leaf
Scanning electron microscope (SEM)Beam of electrons across a
whole specimen (sprayed with fine metal coating)
3 dimensional view of surface features on T.V. screen
100,000x
Scanning Electron Microscope
uses reflected electrons to produce image
Images from a SEM Dentist Drill (x 50)
Hypodermic
Needle (x 100)
Mosquito (x 100)
Toilet
Paper
(x 500)
Phase Contrast: living cells
Blood
Cheek cell
WHICH SCOPE WOULD BE BEST TO USE TO LOOK AT:
A pollen grain
Mold on a piece of bread
Bacteria
Nucleus of a cell
Grasshopper