The Microscope
Science 8: Cells, Tissues, Organs, and Organ Systems
Curriculum Outcomes Addressed:
• Explain that it is important to use proper terms when
comparing plant and animal cells (109-13)
• Compare the early idea that living organisms were made of
air, fire, and water with the modern cell theory (110-2)
• Use a light microscope or micro viewer correctly to produce
a clear image of cells (209-3)
“Micro” = small
“Scope” = to view
http://office.microsoft.com/en-ca/images/results.aspx?qu=microscope&ex=2#ai:MC900382575|
Intro to the Microscope
In this lesson, we will learn about…
– The early idea that living organisms were made up of air,
fire, and water
– The two most common types of microscopes
• Compound Light Microscope
• Scanning Electron Microscope
– The main parts of a compound light microscope
– How to use a compound light microscope to produce a
clear image of specimens
Key Terms
• Microscope: An optical instrument used for magnifying and
viewing very small objects
• Magnification: The degree to which something is enlarged
Power
• Resolution: The amount of detail in an image
• Specimen: A small quantity or sample of something that is
used to represent the larger or original type of its
origin (i.e., drop of blood to represent all blood)
Early Ideas of the Cell Theory
• In ca. 494 BC, ancient Greek philosophers believed that
everything around them was made up of four classical
elements; earth, wind, fire, and water. This belief was
based on the natural observations of the phases of matter
around them.
–
–
–
–
Earth represented everything that was solid
Water represented everything that was liquid
Air represented everything that was gas
Fire represented everything that was plasma
• The Greek Philosopher Aristotle also believed that the
body was made up of four liquids (corresponding to the
four elements); phlegm, blood, yellow bile and black bile,
and that If a person had too much of one of these, they
would fall ill.
http://www.localhistories.org/science.html
Revolution of the Cell Theory
• The first compound microscope was invented in the 1590s by Dutch
spectacle maker Zacharias Jansen.
• In 1658 Jan Swammerdan (Dutch Biologist) first observed red blood
corpuscles.
• In 1661 Marcello Malpighi (Italian Doctor) discovered capillaries
(blood vessels).
• Robert Hooke (English philosopher and architect) was the first
person to describe cells in his book called Micrographia (in 1665).
• Anton van Leeuwenhoek made many contributions in the world of
microscopy (i.e., discovering the vacuole, and is therefore known
worldwide as the “Father of Microscopy” (1723).
• The modern cell theory was first proposed in the 1650s
http://www.localhistories.org/science.html
Types of Microscopes
There are a number of different types of microscopes. We
will focus on the two most commonly used microscopes.
• Compound Light Microscope (Optical Microscope)
• Called “compound” because it is made up of more than one
lens
• Scanning Electron Microscope (SEM)
• Called “scanning electron” because it electrons scan the
topography of a specimen to create and magnify an image
Compound Light Microscope vs. Scanning Electron Microscope
Cost
Method
Light Microscope
Electron Microscope
Usually between $150-$15,000
Very expensive (more than $50,000)
Uses visible light and a system of
lenses to create and magnify images
Uses electrons to scan specimens to
create and magnify images
Magnification Usually between 1000-2000 x at most
Very high (up to 50,000 x)
Resolution
Low resolution (not much detail)
High resolution (a lot of detail)
Image Type
Produces 2D images
Produces clear/detailed 3D images
Advantage
Better for observing living specimen
(i.e., dividing cells, cell movement)
Specimen has to be held in place;
unable to view living specimen
http://en.wikipedia.org/wiki/Optical_microscope
http://upload.wikimedia.org/wikipedia/commons/2/2d/Transmission_electron_microscope_(Philips_TEM)_Mega_View_II_pl.jpg
Compound Light Microscope vs. Electron Microscope Image
Light Microscope
- 2D image
- Low resolution (blurry image)
Electron Microscope
- 3D image
- High resolution (very clear image)
http://2012books.lardbucket.org/books/general-chemistry-principles-patterns-and-applications-v1.0m/section_10_04.html
Compound Light Microscope Image of a Fruit-Fly
http://www2.le.ac.uk/offices/press/press-releases/2011/june/trans-atlantic-team-announce-huntingtons-disease-breakthrough
Electron Microscope Image of a Fruit-Fly
http://www.telegraph.co.uk/science/picture-galleries/7397841/Creepy-crawlies-Amazing-Scanning-Electron-Microscope-pictures-of-insects-and-spiders.html?image=3
Electron Microscope Images of a Snowflake
http://en.wikipedia.org/wiki/Scanning_electron_microscopy
http://en.wikipedia.org/wiki/Scanning_electron_microscopy
The Size of Cells
• The majority of cells are microscopic and cannot be seen with the
unaided eye (without a microscope)
• 1 micrometer (µm) = one millionth of a meter
Interactive Cell Size and Scale: http://learn.genetics.utah.edu/content/begin/cells/scale/
Compound Light Microscope Parts and Functions
Microscope Part
Eyepiece (Ocular Lens)
Body Tube
Arm
Revolving Nosepiece
Objective Lenses
Stage
Function
Allows you to view the image and
contains the ocular lens
The optical path between the eyepiece
and the nearest objective lens
Used to support the microscope when it
is carried; located on the side
Holds the objective lenses and is able to
rotate to change magnification
Found on the nosepiece and range from
low power to high power; these are
what magnify the actual specimen
Supports the slide that is being viewed
Compound Light Microscope Parts and Functions
Microscope Part
Stage Clips
Diaphragm
Function
Used to hold slides in place on the stage
Helps to adjust the amount of light that
reaches the specimen
Coarse Adjustment Knob Moves the stage up and down to help
you get the specimen into view
Fine Adjustment Knob
Moves the stage slightly to help you
sharpen or “fine tune” the specimen
Light Source
Projects light upwards through the
diaphragm to allow you to see the
specimen
Base
The bottom part of the microscope;
allows the microscope to remain stable
Compound Light Microscope Parts
Compound Light Microscope Parts
Proper Use of the Light Microscope
• It is very important to follow instructions on how to carefully use
a microscope. Microscopes can easily be broken, especially when
it comes to the objective lenses.
• Always remember to…
– Carry the microscope with two hands;
one hand holding the arm and one hand
supporting the base
– Check that the low-power objective (the smallest) is in
position over the stage and no closer than 0.5cm to the stage
– Turn both the coarse and the fine adjustment knobs very
slowly when trying to focus on the specimen, and never allow
the objective lens to touch the slide. This can break the slide
and scratch or even break the objective lens
http://www.deftstudios.com/bioweb/images/blab03A.gif
Determining Magnification Power
• Most common light microscope eyepieces are at 10x
• There are usually 3-4 objective lenses (4x, 10x, 40x, 100x)
• In order to determine the magnification power (how many times
you have magnified your image), you must multiply your
eyepiece power (magnification) by your objective lens power
(magnification).
Eyepiece power X Objective lens power = Power of Magnification
Example: If you are using the 4x objective lens…
10x Eyepieces X 4x objective = 40x Final Magnification
Determining Magnification Power: Practice
Q#1: If you are using the 40x objective lens on a microscope that
has a 10x eyepiece, what is your magnification power?
____x Eyepiece X _____x Objective lens = _______x Final Magnification
Q#2: What happens to the image in view as the power of
magnification increases? ______________________________
Determining Magnification Power: Practice
Q#1: If you are using the 40x objective lens on a microscope that
has a 10x eyepiece, what is your magnification power?
10x Eyepieces X 40x objective = 400x Final Magnification
Q#2: What happens to the image in view as the power of
magnification increases? __The image becomes larger__
How to use a Microscope
• Step 1: Place the microscope on the table with the arm facing your body.
• Step 2: Make sure that the low-power objective (smallest objective lens)
is in position over the stage (facing the stage) and no closer than 0.5cm
• Step 3: Rotate the diaphragm to get your optimum light
• Step 4: Place your slide on the stage, adjusting it so that the specimen is
directly under the lens – the specimen should be in view when you are
looking through the eyepiece
• Step 5: Focus on the specimen by slowly moving the coarse-adjustment
knob so that the slide is being moved away from the lens.
• Step 6: Rotate the revolving nosepiece so that the medium-power
objective is in position. Focus with the fine-adjustment knob.
• Step 7: Rotate the revolving nosepiece so that the high-power objective
is in position. Focus with the fine-adjustment knob.
• Step 8: When you are finished with the microscope, return to the lowpower objective lens, and remove the slide from the stage.
Helpful Resources
•
Interactive Microscope Tutorial (Parts and Functions):
http://www.microbelibrary.org/images/jones/player.html
• Microscope parts and functions:
http://sciencespot.net/Media/microparts.pdf
• How to properly use a microscope:
http://www.microscope-microscope.org/basic/how-to-use-a-microscope.htm
•
Microscope parts and functions quiz:
http://www.purposegames.com/game/microscope-parts-functions-quiz
•
Interactive Microscope Online:
http://www.udel.edu/biology/ketcham/microscope/scope.html