MICROSCOPE CALCULATIONS
A) Microscope Magnification = Ocular Lens X Objective Lens
Ocular lens:
10x
Low power objective:
4x
Medium power objective:
10x
High power objective:
40x
What is the magnification under low power?
What is the magnification under medium power?
What is the magnification under high power?
B) Measuring Low Power Field Diameter (field of view): the distance from one side to the other under each power when
looking through the microscope.
Low power: use a ruler to measure it. Use this distance for High & Medium field diameter calculations as follows.
Ex: low power field of view when measured with a ruler = 5 mm
5 mm across
C) High & Medium field diameter must be calculated
This formula is based upon the fact that the ratio of the diameters of the field of view is inversely proportional to the ratio of
the magnifications.
ie
if the diameter doubles, the magnification is halved
ie
if the magnification doubles, the field diameter is halved
Using the formula:
Diameter of high power = magnification of low power
Diameter of low power
magnification of high power
or
DH = ML
DL MH
The diameter under high power = magnification of low X diameter of low
mag high
so,
DH = ML x DL = 40x X 5 mm = 0.5 mm
MH
400x
so, the field diameter of high power is 0.5 mm
Find the diameter of the field of view when using medium power.
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Dm = M L
DL MM
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Using the formula:
Diameter of medium power = magnification of low power
Diameter of low power
magnification of medium power
or
DM = ML
DL MM
DM = ML x DL = 40x X 5 mm = 2 mm
MM
100x
D)
so, the field diameter of medium power is 2 mm
ACTUAL SIZE : Estimating the actual size of object in the field of view:
Multiply the fraction that the object occupies in the field of view by the microscope field of view diameter.
Ex: If 10 organisms could fit across the medium power field of view, the fraction of field of view occupied by the
object is 1/10.
actual size
To calculate its actual size we use the formula: Actual size = fraction of field of view occupied X field diameter
or As = Ffo X Fd
Actual size = 1/10 x 2 mm = 0.2 mm
so, the actual size of the organism is 0.2 mm
E)
Drawing Magnification:
You make an enlarged drawing of your organism. The drawing is obviously much bigger then the actual size of the
organism (you need a microscope to see it.) How many times larger or smaller your drawing is compared to the actual size
of the organism is the drawing magnification.
ie: if you draw the organism 2 cm but its actual size is really only 1 mm, what is the magnification of the drawing?
Use the formula
magnification of drawing = drawing size
actual size
or
Dm = Ds = 2 cm__ = 20 mm = 100x
As
0.2 mm
0.2 mm
so, you drew the organism 100 times larger then it really is.
actual size
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MICROSCOPE _______________
A) Microscope Magnification = _______________ Lens X _______________Lens
Ocular lens:
10x
Low power objective:
4x
Medium power objective:
10x
High power objective:
40x
What is the magnification under low power?
What is the magnification under medium power?
What is the magnification under high power?
B) Measuring ___________ Power Field Diameter (field of view): the distance from one side to the other under each power
when ___________through the microscope.
______power: use a ________to ___________it. Use this distance for ___________& ___________field diameter
___________as follows.
Ex: ________power field of view when measured with a ____________= 5 mm
5 mm across
C) ____________& __________field diameter must be ____________
This formula is based upon the fact that the ________of the diameters of the field of view is ___________proportional to the
ratio of the magnifications.
ie
if the ____________doubles, the magnification is ______________
ie
if the ____________doubles, the field diameter is ___________
Using the formula:
Diameter of high power = magnification of low power
Diameter of low power
magnification of high power
or
DH = ML
DL MH
The ______________under high power = magnification of low X diameter of low
mag high
so,
DH = ML x DL = 40x X 5 mm = 0.5 mm
MH
400x
so, the field diameter of high power is 0.5 mm
Find the diameter of the ____________ of view when using _____________power.
Dm = M L
DL MM
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Using the formula:
Diameter of medium power = magnification of low power
Diameter of low power
magnification of medium power
or
DM = ML
DL MM
DM = ML x DL = 40x X 5 mm = 2 mm
MM
100x
D)
so, the __________ diameter of medium power is 2 mm
_______________ SIZE : Estimating the __________size of _______________in the field of ____________:
Multiply the ____________that the object ______________in the field of view by the microscope field of view _________.
Ex: If 10 organisms could ______across the ___________power field of view, the ____________of field of view
occupied by the object is 1/10.
actual size
To calculate its actual ________ we use the formula:
Actual size = _________of field of view occupied X field ________
or As = Ffo X Fd
_________ size = 1/10 x 2 mm = 0.2 mm
so, the actual size of the organism is _________
E)
__________Magnification:
You make an ____________drawing of your ______________. The drawing is obviously much _____________then the
actual size of the organism (you need a microscope to see it.) How many times _____________or smaller your
____________is compared to the actual _____________of the organism is the ____________magnification.
ie: if you draw the organism ___________but its actual size is really only _________, what is the ______________of the
drawing?
Use the formula
__________ of drawing = drawing _____ or
actual size
___ = Ds = ______ =
As
0.2 mm
so, you drew the organism 20 times ____________ then it really is.
actual size
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20 mm = _____x
0.2 mm