Chapter 3
Microscopes
Essential Questions
• What is the difference between a light
microscope & an electron microscope?
– Know what each type would be used for.
• What is proper care and use of the
microscope?
Microscope Men of History
• 1665: Robert Hooke looked at a sliver of
cork under a microscope and noticed
some “pores” or “cells” in it. Coined the
term cell.
• 1674: Anton van Leeuwenhoek built a
simple microscope with one lens to look at
blood, yeast, and bacteria cells. First to
see living things under the microscope,
animalcules.
Microscope Parts
Eyepiece
Revolving Nosepiece
Arm
Objective Lenses
Stage
Diaphragm
Stage Clips
Coarse Adjustment
Fine Adjustment
Light Source
Base
Microscope Care
• Always use two hands to carry the scope, one on the
arm, one on the base.
• The stage should be placed all the way down, an
objective lens placed on scanning power (red) when
putting away.
• Make sure to wrap up the cord and place the cover over
the top of the microscope when finished.
• Always grab appropriate microscope for the station you
are at, and put away in appropriate spot in cabinet.
• Lens paper is the only tissue that can be used when
cleaning the eyepiece.
How To Use The Microscope
1.
2.
3.
4.
5.
*
Place the slide under the stage clips on the
microscope, with the image in the center of the viewing
field.
Start with the microscope on the scanning power (red).
Look into the eyepiece and use the coarse adjustment
to focus the image so it is clear.
Adjust nosepiece to low power (yellow), and again use
the coarse adjustment to focus the image.
Adjust nosepiece to high power (blue), and this time
use the fine focus to adjustment to focus the image.
If image appears to dark or too light, use the diaphragm
to adjust the amount of light that passes through the
image.
Drawing Specimens
• Use pencil, and take your time.
• All drawings should be drawn
as seen. If in color, draw in
color. Also draw to scale. The
circle represents the field of
view, if your specimen takes
up the whole view, make sure
your drawing reflects that.
• All drawings should include
clear and proper labels,
specimen name, and
magnification.
Example:
Amoeba
400x
Microscope Terms to Know
• Magnification: ability to make an object appear
larger
– The objective lenses are used to increase
magnification.
– The Light microscope has 3 magnifications:
Scanning, Low and High. Each objective will have its
own magnification. In addition to this, the ocular lens
(eyepiece) has a magnification.
– The total magnification is the ocular x objective
• Example: Low Power = 10x and Eyepiece is 10x, total
magnification = 10 x 10 = 100x
Terms cont.
• Resolution: ability to make an object
appear more clear
– To increase resolution the fine and coarse
adjustment is used.
Microscope Types
1. Light Microscope:
the models found in
most schools, use
compound lenses
and light to magnify
objects. The lenses
bend or refract the
light, which makes
the object beneath
them appear closer.
Stereoscope
• This microscope
allows for binocular
(two eyes) viewing of
larger specimens.
(The spinning
microscope at the top
of this page is a
stereoscope)
• Used in dissections
Scanning Electron Microscope
• Allow scientists to
view a universe too
small to be seen with
a light microscope.
SEM’s don’t use light
waves; they use
electrons (negatively
charged electrical
particles) to magnify
objects up to two
million times.
Transmission Electron Microscope
• Also uses electrons,
but instead of
scanning the surface
(as with SEM's)
electrons are passed
through very thin
specimens.