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
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
D
H
=
M
L
D
L
M
H
The
diameter
under high power = magnification of
low X diameter of low
mag high
so,
D
H
=
M
L
x D
L
=
40
x
X 5 mm
= 0.5 mm
so, the field diameter of
high
power is 0.5 mm
M
H
400
x
Find the diameter of the
field
of view when using
medium
power.
D
m
= M
L
D
L
M
M
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