Title: Magnification

1
Title Magnification

• Lesson Objectives
• 1. Can I calculate magnification, image size and
  actual size of a cell? Grade C-A

Starter Recap quiz.
2
Recap quiz

• What is the difference between a micrometer and
  micrometre?
• How many micrometres in a millimetre?
• What is the unit after micrometre?
• How many micrometres in a nanometre?
• Calculate the calibration
• X4 objective lens and a x10 eyepiece ()
• Micrometer is 1mm long with 100 divisions (what
  is each division worth?)

3
Magnification
Photomicrographs often have magnification bars to
allow calculation of the actual size of
specimens.
4.55µm
4
The Magic Triangle.

• I Image size
• A Actual size
• M Magnification
• Remember I AM

I

x
A
M
5
Magnification
In this exercise you will calculate the
magnification and/or true size of the following
1
2
3
4
5
8
6
7
10
9
6
Before we begin

• Note
• Numbers written like this 1.26 x 105 mean you
  move the decimal point to the right. In this
  case you move it 5 times
• 1.26 x 105 126000.0

1.2 6 0 0 0 0
.
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Before we begin

• Note
• Numbers written like this 1.26 x 10-5 mean you
  move the decimal point to the left. In this case
  you move it 5 times
• 1.26 x 10-5 0.0000126

0.0 0 0 0 1.2 6
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Have a go at these
14500.0

• 1.45 x 104
• 0.37 x 107
• 86.41 x 10-3
• 2.65 x 10-2

3700000.0
0.08641
0.0265
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Figure 5.1 Paramecium caudatum
x600
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Figure 5.1 Paramecium caudatum
Measured length 142mm
142 600 0.237mm
0.237mm 237µm
x600
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Figure 5.2 chloroplasts
x9000
12
Figure 5.2 chloroplasts
Mean measured length of the four largest
chloroplasts 39.25mm
39.25 9000 0.0044mm
0.0044mm 4.4µm
x9000
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Figure 5.3 a bacterium
Measured length 128mm
128 0.002mm magnification
Magnification x64000
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Figure 5.4 seven week human embryo
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Figure 5.4 seven week human embryo
Measure the actual length of the scale bar and
divide by the length it represents
Magnification 25 10 x2.5
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Figure 5.5 head of a fruit fly
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Figure 5.5 head of a fruit fly
Measure the actual length of the scale bar and
divide by the length it represents
Magnification 12.5 0.2 x62.5
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Figure 5.6 pollen grain
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Figure 5.6 pollen grain
(a) Measure the actual length of the scale bar
and divide by the length it represents
Magnification 25 0.02 x1250
(b) 47mm
(c) 47 1250 0.0376mm
0.0376mm 37.6µm
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Figure 5.7 red blood cells in an arteriole
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Figure 5.7 red blood cells in an arteriole
Measured length of scale bar 30mm
Magnification 30 0.01 x3000
Diameter 25mm approx
Actual diameter 25 3000 0.0083mm
0.0083mm 8.3µm
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Figure 5.8 a mitochondrion
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Figure 5.8 a mitochondrion
Measured length of scale bar 30mm
Magnification 30 0.002 x15000
Measured width 34mm
Actual width 34 15000 0.0023mm
0.0023mm 2.3µm
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Figure 5.9 bacteriophage a type of virus
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Figure 5.9 bacteriophage a type of virus
Measured length of phage 29mm
Magnification 29 0.0002 145000
Magnification 1.45 x 105
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Figure 5.10 potato cells
starch grains
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Figure 5.10 potato cells
Mean diameter of the cells 38mm approx
Measured length of scale bar 24mm
Magnification 24 0.1 x240
Diameter of the cells 38 240 0.158mm
0.158mm 158µm
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Magnification.

• The resolving power of the unaided eye is
  approximately 0.1mm
• The maximum useful magnification of light
  microscope is around x1500
• Plant and animal cells typically measure around
  20µm
• Many organelles are as small as 25nm beyond the
  resolving power of the light microscope
  wavelength of light is 500nm approx
• Wavelength of electron beam is 0.005nm
• Maximum resolving power of the electron
  microscope is 0.2nm

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Question 11.
Structure Size Kind of structure Visible at x1500?
bacteriophage 0.2µm virus ?
bacterium 2.0µm prokaryotic cell ? (just)
mitochondrion 2.3µm eukaryotic organelle ?
chloroplast 4.4µm eukaryotic organelle ?
red blood cell 8.3µm eukaryotic cell ?
pollen grain 38µm eukaryotic cell ?
potato cell 158µm eukaryotic cell ?
paramecium 237µm eukaryotic organism ?
embryo 30mm eukaryotic organism ?