SME
Grade 6 Science · Problem type
Cell size from the field of view
Use this for “About 20 cells fit across a 2,000 µm (2 mm) field. How long is one cell?”
Diagram
6 cells fill 1,800 µm end to end.
This is an example. Type your own values to start a new problem.
Width of the field of view
example · µm
Cells across
example
Cell length
calculated · µm
Formulas
1,800 ÷ 6 = 300
Width of the field of view ÷ cells across = cell length
Assumptions
•
A micrometer (µm) is a thousandth of a millimeter. Most cells are 10 to 100 µm long; onion skin cells are bigger, about 200 to 400 µm.
•
With a 10× eyepiece the circle is about 4,500 µm across at 40×, 1,800 µm at 100× and 450 µm at 400×.
•
Count the cells end to end across the middle of the circle.
Step-by-step
WE KNOW
Width of the field of view: 1,800 µm
Cells across: 6
FIND
cell length
Step 1 · Find cell length
1,800 ÷ 6 = ?
Width of the field of view ÷ cells across = cell length
The cells end to end fill the circle, so share its width among them.
Cell length = 300 µm
Check
Put the numbers back in. Both sides should match.
6 × 300 = 1,800 ✓
Topic check
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