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Title: Magnification. Lesson Objectives : 1. Can I calculate magnification, image size and actual size of a cell? Grade C-A. Starter : Recap quiz…. Recap quiz…. What is the difference between a micrometer and micrometre? How many micrometres in a millimetre?

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Title magnification
Title: Magnification

Lesson Objectives:

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

Starter: Recap quiz….


Recap quiz
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?)


Magnification
Magnification

Photomicrographs often have magnification bars to allow

calculation of the actual size of specimens.

4.55μm


The magic triangle

I – Image size

A – Actual size

M – Magnification

Remember: I AM

The Magic Triangle….

I

÷

x

A

M


Magnification1
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


Before we begin
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

1.260000

.


Before we begin1
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

0.00001.2 6


Have a go at these
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


Figure 5 1 paramecium caudatum
Figure 5.1 Paramecium caudatum

x600


Figure 5.1 Paramecium caudatum

Measured length = 142mm

142 ÷ 600 = 0.237mm

0.237mm = 237μm

x600


Figure 5 2 chloroplasts
Figure 5.2 chloroplasts

x9000


Figure 5.2 chloroplasts

Mean measured length of the four largest chloroplasts = 39.25mm

39.25 ÷ 9000 = 0.0044mm

0.0044mm = 4.4μm

x9000


Figure 5.3 a bacterium

Measured length = 128mm

128 ÷ 0.002mm = magnification

Magnification = x64000


Figure 5 4 seven week human embryo
Figure 5.4 seven week human embryo


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


Figure 5 5 head of a fruit fly
Figure 5.5 head of a fruit fly


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


Figure 5 6 pollen grain
Figure 5.6 pollen grain


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


Figure 5 7 red blood cells in an arteriole
Figure 5.7 red blood cells in an arteriole


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


Figure 5 8 a mitochondrion
Figure 5.8 a mitochondrion


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


Figure 5 9 bacteriophage a type of virus
Figure 5.9 bacteriophage [a type of virus]


Figure 5.9 bacteriophage [a type of virus]

Measured length of phage = 29mm

Magnification = 29 ÷ 0.0002 = 145000

Magnification = 1.45 x 105


Figure 5 10 potato cells
Figure 5.10 potato cells

starch grains


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


Magnification2
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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