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?
Magnification
enlargement of an object
 compare size of image to actual size of
object

total magnification

ocular power x objective power = total
magnification
Microscopes
Microscopes
Resolution –
capacity to show 2
points that are close
together as separate
.
10x
..
1000x
Poor Resolution = Blurry Image
Good Resolution = Clear Image
Resolution
How does a microscope
work?
Parfocal
both low and high power objectives are
adjusted to the same focus
 easily 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 thru
can use live specimens
usually doesn’t exceed
total mag. of 2000x
Our scopes in class are
capable of 400x
only 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 Microscope
Stage – 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 Types
Scanning electron microscope (SEM)
 Transmission electron microscope (TEM)

Electron Microscope
Discovered 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