Download Magnification and Size

Magnification and Size
Measuring biological specimens
using millimetres as units
To accurately measure the size of cellular
structures we need a suitable scale:
Ideally, we need a scale we can see directly
alongside the cells we are observing:
Start by putting a ruler under the microscope:
Appearance of ruler at medium magnification
Appearance of tissue at medium magnification
Estimating cell size at medium magnification
12
1 mm
1mm / 12 cells =
0.083 mm
5
1mm / 5cells=
0.2 mm
1 mm
Other units
Diameter of field
of view/mm
No. of cells
lengthways
No. of cells
widthways
Mean length (mm)
Mean width (mm)
1.00
5
12
0.2
0.083
1mm = 1000µm
Mean length of cells = 0.2 x 1000 = 200µm
Mean width of cells = 0.083 x 1000 = 83µm
Calculating actual size:
Calculating magnification & actual size:
Calculating actual size:
Calculating magnification:
Calculating magnification & actual size:
Calculating actual size:
Cell Magnification
This diagram shows the general
structure of an animal cell from
an electron microscope.
Calculate the magnification
factor.
Calculate the length of G - a
mitochondrion.
Calculate the diameter of the
nucleus.
____ 0.005 mm
Calculate the width of the cell at
its widest part.
Plant cell magnification
Diagram shows the
generalised structure of a
plant cell as seen with an
electron microscope.
Calculate the magnification
factor.
Calculate the width of the cell.
Calculate the length of the
vacuole.
____
0.040 mm
Magnification of an Illustration = Size
of Illustration / Actual Size
For example, a magnification of 1x means the
illustration is the same size as the object, 100x
means the illustration is 100 times bigger than the
object, etc. It is important that you first calculate or
measure the actual size of an object, and from that
calculate the magnification of the illustration .
Always draw the magic triangle and fill in the
information you have.
Always check your units.
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see thi s picture.