Laboratory
Exercise 1
How to Use a
Compound Microscope
Basic Microscopy
Image: The Far Side by Gary Larson
Compound Light Microscope
Scanning electron Microscope
Transmission electron Microscope
Compound Light Microscope
The “Compound” Part
• Simple microscopes have single magnifying lens
glass).
(like a magnifying
• Compound microscopes have two sets of lenses for
magnification.
• Lens closer to the eye = ocular/eyepiece lens
of 10x).
(magnifying power
• Lenses closer to the object being viewed = objective lens.
(Most light microscopes used in biology have three or four objective lenses).
The “Light” Part
• Bright-field light microscopes produce a dark image against
brighter, backlit background.
• Provide a 2-D image.
• Commonly used to view stained cells.
Parts of a Compound Light Microscope
Resolution
The smallest distance at which two points
can be seen separately.
Refraction
When the light source passes through the
slide from below, and then enters the air, the
light is bent, and goes off to one side or the
other. This bending is called refraction
Depth-of-filed
The vertical distance that is in focus at any
time.
Filed-of-view
It refers to how much of your sample or the
area of your sample you can see at one time.
Parfocal lens
If you change your object lens from one to
the other, you will still have your specimen in
focus without having to focus more than a
little.
Depth-of-filed
The vertical distance that is in focus at any
time.
Magnification & The Objective Lenses
Ocular lens magnifies the specimen 10x.
You will always be looking through the ocular
and objective lens simultaneously, so
multiply ocular magnification x objective
power to calculate the Total Magnification
(xTM).
Rotary nosepiece of your microscope has
four objective lenses attached.
Shortest lens (red band) should have been
pointing down when your scopes were last
put away.
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port
Scanning Power Objective Lens
• Red band around it.
• Magnifies objects 4x.
• Q: What is the Total
Magnification? ____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port
Low Power Objective Lens
• Has yellow band around it.
• Magnifies objects 10x.
• Q: What is the Total Magnification?
____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port
High Dry Objective Lens
• Has blue band around it.
• Magnifies objects 40x.
• Q: What is the Total
Magnification? ____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port
Procedure
Let’s go over it together!
40X TM
100X TM
400X TM