Microscopes
What is a Microscope?
• A device for forming a magnified
image of a small object.
• An optical instrument used for
producing a magnified image of a
small object.
• A device that allows a small object to
be viewed under high magnification.
Did You Know . . . ?
• The microscope is
the most important
tool for biologists.
• The first cells were
seen in 1663.
• The first
microscope was
made in 1950.
The Beginnings
• Of the five senses, the most important is sight.
– Aids in the process of gathering information about the
environment that we are part of. However, this is
adequate only to a certain point.
– Beyond this point, the human unaided eye fails to help
us; the amount of detail that it can provide is severely
limited.
• In order to overcome those limitations, humans
started to develop instruments like the
magnifying glass, the spectacles, the telescope
and the microscope.
Founding Fathers of
Microscopy
• Hans and
Zacharias Janssen
• Robert Hooke
• Anton von
Leeuwenhoek
Hans and Zacharias Janssen
• Credit for the first microscope
is usually given to Zacharias
Janssen, around the year
1595.
• Since Zacharias was very
young at that time, it's
possible that his father Hans
made the first one, but young
Zach took over the
production.
• The first compound
microscopes produced by the
Janssen's was simply a tube
with lenses at each end.
• The magnification of these
early scopes ranged from 3X
to 9X, depending on the size
of the diaphragm openings.
Robert Hooke
• Hooke’s remarkable
engineering abilities
enabled him to invent
and improve many
mechanical devices,
including timepieces and
the Gregorian telescope.
• Hooke improved on early
compound microscopes
around 1660.
• In 1665, he coined the
word cell to describe the
features of plant tissue
(cork from bark of an oak
tree).
Anton von Leeuwenhoek
• Leeuwenhoek was a man
with many talents; his
most important attributes
were creativity, power of
observation, and
ingenuity.
• He made simple (one lens)
microscopes.
• He built the best
microscopes for the time
period.
• He was the first person to
describe bacteria (from
teeth scrapings) and
protozoan (from pond
water).
Compound Light Microscope
• Compound
– Deals with the
microscope having
more than one lens.
• Light
– Refers to the method by
which light transmits
the image to your eye.
• Microscope
– “Micro” – small
– “Scope” – view
Terminology
• Objective
• Ocular
• Total
magnification
• Resolution
• Focal Point
• Lens closest to the
specimen.
• Lens you look through.
• The total power of the
microscope (multiply the
magnification of both
lenses).
• The amount of detail you
can see in an image.
• The point at which the
light from a lens comes
together.
How Does it Work?
• Microscopes take an image
of something generally too
small to see with the
naked eye and magnify
that image so that the
observer can see it in
greater detail.
• To magnify images, a
microscope uses several
lenses to change the angle
at which rays of light strike
the eye of the observer.
Parts of the Microscope
Ocular Lens or Eyepiece
• This lens sits directly in front
of the observer's eye and does
not typically change in
magnification power.
• Older-style microscopes were
"monocular," meaning they
had only one eyepiece, but in
recent years microscopes have
been made "binocular" in
order to relieve eyestrain and
allow for more natural
viewing.
Objectives
• The objective lenses
combine with the power of
the ocular lens to create
the magnified image.
• Frequently one starts on
the lowest magnification
to find focus and then
increases magnification
one objective at a time.
• This is facilitated by a
rotating nosepiece that
allows the objectives to be
interchanged smoothly.
Objective Lens
• Objective lenses come in
several varieties.
• In a light microscope, the
lowest power objective
(frequently 4x or 10x) is
referred to as the "scanning"
objective, as it allows the
observer to find an area of
interest before increasing
magnification.
• As magnification increases,
the amount of light collected
from the sample decreases.
For this reason, the highest
objective on a light
microscope (such as the 100x)
requires mineral oil to be
applied to the gap between
lens and sample. The oil has a
greater refractive index and
bends more light into the
objective.
Coarse Adjustment Knob
• Both knobs change the
distance between
objective and viewing
sample.
• The coarse adjustment
knob is primarily used with
the scanning objective.
• It allows the user to bring
the scope into
approximately the right
plane of focus.
• Once this has occurred, it
is preferential to leave the
coarse adjustment alone
and use only the fine
adjustment.
Fine Adjustment Knob
• The fine adjustment
knob helps clarify a
partially focused
image.
• It requires many more
turns than the course
adjustment to do the
same amount of work.
• This allows the
observer to take great
care in clarifying the
image.
Stage
• The stage, usually adorned
with stage clips of some
sort, is where the specimen
rests.
• After being centered over
a hole in the middle and
secured with the clips, the
subject can be raised or
lowered by the course and
fine adjustment knobs.
• Also, the stage has its own
controls for moving the
subject left, right, back,
and forward on the
horizontal plane.
Light Source
• The light source sits at
the base of the
microscope (usually)
and either consists of
a radiant bulb or a
mirror for redirecting
light.
• Light is shined up
through the hole in
the stage to illuminate
the sample.
Diaphragm
• Before the light enters the
stage opening, it passes
through the diaphragm.
• The diaphragm, which has
an opening or "aperture" in
the form of an iris, only
allows light to pass
through its center.
• By increasing or shrinking
the size of the iris, you can
control how much light
passes through to the
sample.
• The light is condensed in
order to create the highest
level of clarity to an image.
The Body - Base & Arm
• The "body" of the
microscope is divided into
two parts: the base and the
arm.
• The base is heavy and
prevents the scope from
slipping on the bench top
or tipping over.
• The arm holds all of the
apparatus in place above
the light source.
• A microscope should
ALWAYS be carried by
both the base and the arm.
Microscope Care & Handling
• Transporting
• Handling
• Cleaning
• Storage
• Grab the arm with one hand
and place your other hand on
the bottom of the base.
• Never touch the lens with
your fingers.
• Only use lens paper to clean
the glass.
• Put the low power objective
in place and the stage all the
way up.
Using the Microscope
Before You Start
• Place the microscope on a table with
the arm towards you about a fist’s
length from the edge of the table.
• The microscope should be on the
lowest power objective and the stage
should be all the way up.
• The diaphragm should be set on the
brightest field of view.
Using the Microscope
First Focusing
• Place a slide on the stage centering
the specimen over the stage
opening.
• Use the stage clips to hold the slide
in place.
• Looking through the eyepiece,
slowly turn the coarse adjustment
knob until the specimen comes into
focus.
Using the Microscope
Switching Objectives
• Look at the microscope from the side.
• Carefully revolve the nosepiece until the
high-power objective lens clicks into place.
• Make sure the lens does not hit the slide.
• Looking through the eyepiece, use the
fine adjustment knob until the specimen
comes into focus.
Cool Microscopic Images
Cool Microscopic Images
Cool Microscopic Images
The Magnificent Microscope