The Microscope
Oct. 13, 2010.
HOMEWORK tonight: microscope
worksheet
DO NOW: pick up notes and copy
these definitions in your notes
• MICROSCOPE: An instrument for
making an enlarged image of an
object which is too tiny to be seen
by the “naked” eye.
• LENS: a piece of glass or plastic that
bends light rays causing them to
come together or move away from
each other to form an image.
Brief History
• Mid 1500s –First microscope.
– A Dutch reading glasses maker put 2 magnifying glasses
together in a tube to get a larger image than either lens
alone.
• Mid 1600s – Anton van Leeuwenhoek
– Improved the microscope; magnified objects 270 times
their original size
– Using his microscopes, he was the first to observe and
describe single celled organisms, which he originally
referred to as animalcules (we now refer to them as
microorganisms!).
Types of Microscopes
• Simple microscope: Use ONE lens.
– Example: Magnifying glass.
• Compound light microscope--named because they use two
or more lenses to magnify objects.
– Highest possible magnification is 1,000X
– THIS IS WHAT WE USE IN CLASS
• Electron Microscope --Do not use lenses to direct light;
they use electrons (negatively charged electrical particles)
to magnify objects up to 2,000,000X!!!
– allow scientists to view things too small to be seen with a light
microscope.
– Used to observe atoms and molecules
Electron Microscope
Compound Microscope
Insects using Electron Scan
Microscope!!
• Regular picture
of an insect
PARTS of a Microscope
• Eyepiece Lens: the lens at the top that you look
through.
• Body Tube: Connects the eyepiece to the objective
lenses.
• Objective Lenses: Usually you will find 3 or 4 objective
lenses on a microscope. They almost always consist of
4X, 10X, 40X and 100X powers.
• Nosepiece: This is the part that holds the objective
lenses and can be rotated to change power.
• Base: The bottom of the microscope, used for support.
• Arm: Supports the tube and connects it to the base
• Light source: found near the base of the microscope;
makes the specimen easier to see.
• Stage: The flat platform where you place your slides.
• Stage clips: found on the stage; hold the slides in
place.
• Diaphragm: rotating disk under the stage; different
sized holes vary the intensity and size of light that is
projected upward into the slide.
• Coarse adjustment knob: large, round knob on the side
of the microscope used for focusing the specimen; it
moves the stage up and down.
• Fine adjustment knob: small, round knob on the side
of the microscope used to fine-tune the focus of your
specimen after using the coarse adjustment knob.
Calculating Total Magnification
• Take the power of the objective (4X, 10X, 40x)
and multiply by the power of the eyepiece
(usually 10X).
• You CAN DO IT!!!
• calculating total mag
FIELD OF VIEW
• Field of View: The area of the slide that you
see when you look through a microscope; it is
the circle of light.
Field of View
• When viewing a small organism through the microscope,
it’s usually necessary to have some idea of its size.
Therefore, you need to have some way of estimating the
size.
• When someone is standing near a doorway, you can
estimate their height by comparing them to the doorway.
– Example: If the “doorway is 10 units, how high is the stick person?
• You can estimate an organism’s length the same way,
by comparing it to the field of view that you are using.
SO…how do I find the diameter of the field of
view?
Field of view for higher powers
• Total magnification on low power
• --------------------------------------------• Total magnification on other power