Word of the Day:
Basic Laboratory Skills:
Magnification: the
Making Microscopic
process of enlarging
Measurements
:
Lab
2d
something
MICROSCOPIC MEASUREMENT
AND DRAWING
How big is a cell?
• http://www.cellsalive.com/howbig.htm
How can we determine the
size of a specimen under the
microscope?
• Most accurate:
– Micrometer
• Ruler
• Built into ocular
• Alternative:
– Estimate using
the technique
we will do today!
Our Method - Low Power
• Make a wet-mount of a piece of 1-mm graph
paper (10mm2)
• Count how many millimeters across appear in
your field of view in low power (40X - with
eyepiece)
– Convert to micrometers
– How many micrometers in a millimeter?
– Record this in results!
Making Microscope Measurements
Total view =
2 boxes =
4 mm across=
4000 μm
1 Box = 2 mm
40X
Field of Vision Sizes
• Field of visions for
higher powers are
based off of the 40X
field
• 100X is 2.5 times
smaller then 40X
• 400X is 10 times
smaller then 40X
40X
2.5 times
smaller
10 times
smaller
100X
400X
Fields of Vision
• 40X = 2 boxes = 4 mm  4000 μm
• 100X = 2 boxes/2.5 = .8 boxes = 1.6 mm 
1600 μm
• 400X = 2 boxes/10 = .2 boxes = 0.4 mm 
400 μm
*All measurement are for width across the
middle*
Field of Vision at High
Magnifications
• You know that…
– The field of vision is
~400 μm wide
• You estimate that…
– The cell takes up
about 1/3 of the width
• You can calculate
that…
400X
– The cell is about
133.3 μm
– 400*1/3 = 133.3 μm
Procedure
1. Make a wet mount of mm grid graph paper.
2. Count how many 1-mm square go across
the diameter of the low power field.
3. Convert the diameter measurement from
mm to µm.
1 mm = 1000 µm
4. Create a data table and record the size of
the low power field in both mm and µm
mm
40x
100x
400x
µm
Procedure (cont.)
5. Do the division (do NOT measure!) to calculate the
sizes of the medium and high power fields.
40X
2.5 x smaller
100X
10x smaller
400X
6. Report the values in both mm and µm in data
table
Next!!!!!!!
• Choose a slide and draw your organism
– Use details
– Use shading
– List power drawn under
– Make large
Example
• Paramecium
– 400X