Microscope Basics
Parts of the Microscope
1 . Eyepiece : the part that you look through
(closest to the eye) usually 10x
2. Objective Lens : the magnifying part
closest to the slide (high power=usually 40x;
low power=usually 10x)
3. Fine Adjustment Knob : used to focus on
low & high power
4. Coarse Adjustment Knob : used to focus
only on low power
5. Stage : where the slide is placed
6. Stage Clips : hold the slide in place
7. Diaphragm : controls the amount of light
used
Calculating Magnification
If a microscope has a 10X eyepiece, and 10X
and 40X objectives.
Total Magnification on low power : 10 X 10 =
100X ( it looks 100 times bigger than real life)
Total magnification on high power : 10 X 40 =
400X (it looks 400 times bigger than real life)
Is what we see under a microscope EXACT?
Actual Image
• When we view objects under the
microscope…
1. We see a mirror image that is flipped up
side down.
2. Increasing magnification reduces the field.
(Larger image but you see less of it)
3. Increasing the magnification reduces the
amount of light. (Field darkens)
F
Under microscope
How to make a wet mount slide:
• Put the cells on the center of a slide, put a drop of water with a
dropper onto the cells (do not touch the cells)
• Lower a cover slip slowly at an angle (to reduce the number of air
bubbles)
Too much water? Use a
paper towel to absorb
excess liquid.
Types of Microscopes:
Light microscopes:
- Around 1600
- The ones that WE use!
- Lenses made of glass or plastic
- Maximum = 2000x larger
Types of Microscopes
Electron Microscopes:
-1930
-View molecules and atoms, smaller images than a light microscope
-1st type= Transmission Electron Microscope (TEM)
- beams of electrons
- resolution = 1000x better than light microscope
SEM
- Scanning Electron Microscope
- 1935
- Better depth of view, higher resolution, more detailed surface picture
- resolution: A measure of the clarity of an image; the minimum
distance that two points can be separated by and still be
distinguished as two separate points.
Important Units for Microscopes

Micrometers (microns) = µm
1/1000th of a millimeter
1000 micrometers = 1 mm

How big is a micron? 


Finding Field of View (F.O.V)
Under Low Power: Use millimeter ruler
Ex: 1.5mm
Convert to micrometers
1 mm = 1000 micrometers
So 1.5 mm = 1,500 micrometers
(Move decimal over 3 to right)
Finding Field of View (F.O.V)
• Under Medium or High
Power
Need to set up a
proportion
Low power Magnification = High power FOV
High power Magnification Low power FOV
Remember!!
• As magnification
increases FOV decreases
Ex:
100x
500x
=
HP FOV
1500 micrometers
500x = 150000
HP FOV = 300 micrometers
Practice:
• A student determines that the field of view with a 10 X
ocular and a 4 X objective is 2.1 mm in diameter. What is the
diameter of the field of view with the same ocular and a 40 X
objective?
Determining the Size of an Object Under a
Microscope
1) View and draw object on low power
2) Estimate how many objects would fit across diameter of field of view


Divide the diameter
of FOV by the
number of objects
that can fit across it.
Ex:
– Three letter “e”s fit
across FOV of 1800
micrometers
– Each letter is about
600 micrometers
1800 micrometers = 600 µm
3 letter “e”
Practice:
• 1. What is the primary difference between a low - power objective
and a high - power objective?
• 2. What is the total magnification of a microscope with a 15 X ocular
and a 40 X objective?
STUDENT NOTES
Microscope Basics
Parts of the Microscope
1 . ____________: the part that you look
through (closest to the eye) usually 10x
2. _____________Lens : the magnifying part
closest to the slide (high power=usually 40x;
low power=usually 10x)
3. __________________Knob : used to focus
on low & high power
4. _____________Adjustment Knob : used to
focus only on low power
5. ____________: where the slide is placed
6. ________________: hold the slide in place
7. __________________: controls the
amount of light used
Calculating Magnification
If a microscope has a 10X eyepiece, and 10X
and 40X objectives.
Total Magnification on low power :
( it looks __________times bigger than real
life)
Total magnification on high power :
(it looks 400 times bigger than real life)
Is what we see under a microscope EXACT?
Actual Image
• When we view objects under the
microscope…
1. We see a ________________that is
____________________________.
2. ______________magnification
_________the field. (Larger image but you
see less of it)
3. ______________the magnification
_____________the amount of light. (Field
darkens)
Under microscope
How to make a wet mount slide:
• Put the cells on the _______________, put a _______________ with
a dropper onto the cells (do not touch the cells)
• Lower a cover slip ___________________________(to reduce the
number of air bubbles)
Too much water?
Types of Microscopes:
Light microscopes:
- Around 1600
- The ones that WE use!
- Lenses made of glass or plastic
- Maximum = 2000x larger
Types of Microscopes
Electron Microscopes:
-1930
-View molecules and atoms, smaller images than a light microscope
-1st type= Transmission Electron Microscope (TEM)
- beams of electrons
- resolution = 1000x better than light microscope
SEM
- Scanning Electron Microscope
- 1935
- Better depth of view, higher resolution, more detailed surface picture
- resolution: A measure of the clarity of an image; the minimum
distance that two points can be separated by and still be
distinguished as two separate points.
Important Units for Microscopes

Micrometers (microns) = µm
1/1000th of a millimeter
1000 micrometers = 1 mm

How big is a micron? 


Finding Field of View (F.O.V)
Under Low Power: Use millimeter ruler
Ex: 1.5mm
Convert to micrometers
1 mm = _______________________
So 1.5 mm = 1,500 micrometers
(Move decimal over _______________)
Finding Field of View (F.O.V)
• Under Medium or High
Power
Need to set up a
proportion
Low power Magnification = High power FOV
High power Magnification Low power FOV
Remember!!
• As magnification
increases FOV decreases
Ex:
100x
500x
=
HP FOV
1500 micrometers
500x = 150000
HP FOV = 300 micrometers
Practice:
• A student determines that the field of view with a 10 X
ocular and a 4 X objective is 2 .1 mm in diameter. What is the
diameter of the field of view with the same ocular and a 40 X
objective?
Determining the Size of an Object Under a
Microscope


1) ________and ____________object on low power
2) _____________how many objects would fit across diameter of field
of view
Divide the diameter
of FOV by the
number of objects
that can fit across it.
Ex:
– Three letter “e”s fit
across FOV of 1800
micrometers
– Each letter is about
600 micrometers
Practice:
• 1. What is the primary difference between a low - power objective
and a high - power objective?
• 2. What is the total magnification of a microscope with a 15 X ocular
and a 40 X objective?