Name:_______________________ Date:_____________
HOW TO DETERMINE DRAWING MAGNIFICATION
1.
Measure your low power field of view (FOV) using the mm scale on a clear ruler. Ex: 4.5mm
2.
Make note of Low, Medium and High power magnification. Ex. Low = 4x, Medium 10X, High 45X
3.
Calculate the field of view for medium and high power.
Example:
If the power magnification on Low = 4x and the FOV = 4.5 mm, then you can figure out
the FOV for medium and high using the following method:
Medium
High
4.
10x
40x
FOV = 4.5 mm x (4/10) = 1.8 mm
FOV = 4.5 mm x (4/40) = 0.45 mm
Look at the specimen and estimate how many specimens
will fit across the diameter of the field.
Example: 6.5 specimens (widthwise) fit
across the HIGH power field
5.
Calculate the actual size of the specimen.
Actual Size =
field of view
# of specimens across(width or length?)
Actual Size =
0.45 mm
6.5 specimens (w or l?)
= 0.069 mm / specimen (w or l?)
6.
Draw your specimen using the drawing rules.
7.
Measure your specimen drawing in mm. Use the same dimension as used in
estimating the number of specimens across the field of view (i.e. width or length).
8.
Calculate the magnification of your drawing.
Drawing Magnification =
Drawing Measurement (mm) (width or length?)
Actual Size (mm) (width or length?)
= 20mm ÷ 0.069mm
= 290 X (round to whole number)
Drawing Magnification Problem Set
Use the estimated fields of view of the microscopes to complete the following questions.
(High 40x FOV = 0.45 mm)
1. A cell is observed to stretch half way across the high power field. How
long is the cell?
2. Many ponds often have a green scum on the surface. This scum is a tangled
mass of stringy algae filaments. Looking at a filament under high power
shows four cells arranged end to end across the field of view.
a. What is the diameter of the high power field of view in millimeters?
b. How long is each cell approximately?
3. 15 cells are observed across the centre of the high power field. How long is each cell?
4. A cell is observed under high power to be about half the field diameter. A student draws the cell 25cm in
length. What is the magnification of the drawing?
5. A student draws a cell diagram 24mm long. She writes 400X below the diagram. How large is the actual cell?
6. A cell is 80 m in length. If drawn 600 times actual size, how long will the drawing be in cm? (HINT: 1 micrometer
= 0.001 millimeters)
7. 5 onion cells are counted across the centre of the high power field. One cell is drawn 18mm long. Calculate
the drawing magnification.
8. 40 potato cells are counted across the centre of the medium field of view. One cell is drawn 2cm long. What
is the drawing magnification?
9. The diameter of a hair is estimated to be one tenth of the diameter of the medium power field. It is
drawn 4cm wide by a student. What is the drawing magnification?
10. Copy the chart and complete:
Drawing Size
10mm
Actual Size
100mm
Drawing Magnification
4mm
3X
10cm
25X
150mm
15mm
0.8cm
8mm
Drawing Magnification Problem Set Answers
1. high power FOV = 0.45 mm
2. a. high power FOV = 0.45 mm

AS = 0.45 mm ÷ 2 = 0.225 mm
b. AS = 0.45 mm ÷ 4 = 0.1125 mm
3. high power FOV = 0.45 mm  AS = 0.45 mm ÷ 15 = 0.03 mm
4. high power FOV = 0.45 mm  AS = 0.45 mm ÷ 2 = 0.225 mm 
DM = 250 mm ÷ 0.225 mm = 1111 X
5.
DM = DS ÷ AS
400 X = 24 mm ÷ AS
AS = 24 mm ÷ 400
AS = 0.06 mm
6. AS = 80 micrometres = 80 x 10-6 metres = 80 x 10-4 centimetres = 8 x 10-3 cm
DM = DS ÷ AS
600 X = DS ÷ 8 x 10-3 cm
DS = (600)(8 x 10-3 cm)
DS = 4.8 cm
7. high power FOV = 0.45 mm  AS = 0.45 mm ÷ 5 = 0.09 mm 
DM = DS ÷ AS 
DM = 18 mm ÷ 0.09 mm = 200 X
8. low power FOV = 4.5 mm  medium power FOV = 4.5 mm (4/10) = 1.8 mm
AS = 1.8 mm ÷ 40 = 0.045 mm
DM = DS ÷ AS 
DM = 20 mm ÷ 0.045 mm = 444 X
9. medium power FOV = 4.5 mm (4/10) = 1.8 mm
AS = 1.8 mm ÷ 10 = 0.18 mm
DM = DS ÷ AS 
DM = 40 mm ÷ 0.18 mm = 222 X
10. DM = DS ÷ AS
Drawing Size
Actual Size
Drawing
Magnification
10mm
100mm
0.1X
12 mm
4mm
3X
10cm
0.4 cm
25X
150mm
15mm
10X
0.8cm
8mm
1X