1. Quick Questions
1. Using your ruler, find something in this room that is:
5 cm
5 mm
0.2 m
30 mm
2. Order the following from smallest to greatest:
1 meter
1 centimeter
1 kilometer
1 inch
1 millimeter
1 decimeter

2. Announcements Past Due: Due Today: Remember:
Kingdom Classification
Due Today:
Cell Worksheet
Last Day to Take Quiz
Remember:
Corrections Due This Week (except for G)

3. Today’s Topics By the end of this lesson you should be able to:
Magnification and Scale
Units of Measurement
Resolution vs. Magnification
Types of Microscopes
By the end of this lesson you should be able to:
Explain the difference between magnification and resolution.
Calculate the magnification /actual size of an image.
Describe the advantages and disadvantages of obtaining images using a: light microscope, transmission electron microscope, scanning electron microscope.

4. UNITS of Measurement

5. You must know mm for IGCSE Co Sci
Units of Measurement
(In cell studies)
Unit
Symbol
Fraction of a meter
Meter m
= 1
Centimeter cm
= 10-2 m
Millimeter mm
= 10-3 m
Micrometer μm
= 10-6 m
Nanometer nm
= 10-9 m
You must know mm for IGCSE Co Sci
Human cells: 5-40 µm
Mitochondria: ~1µm
Ribosomes: ~25nm

6. X 1000
(m)
(mm) 2m 2
2000 (2 x 103)
130cm
1.3
1300
0.032m
0.032
32 (3.2 x 10)
7.25mm
7.25
÷ 1000

7. Independent Practice
Silently, in your notebook, convert each of the following to millimeters (mm).
a)     3.5 cm
b)     4.0 m
c)      1.5 m
d)     0.5 cm

8. Magnification and Scale

9. Magnification
Magnification is how much larger an image is compared with the real size of the object
Analogy: high school drama

10. Magnification. Magnification = I observed size (image size)
A actual size (real size of structure)
You must measure from the edge of the structure and be consistent.
Then divide the number you get by the size of the structure you have been given.
You can rearrange this:
Actual= I size of structure in picture
size M magnification

11. Example 1
A leaf is 3 cm long. A student made a drawing of the leaf, which was 6 cm long. What was the magnification of the drawing?
real size = 3 cm size in drawing = 6 cm
magnification =6cm/3cm =  2
Notice that there are no units with the magnification.
Magnification is always written as x a number.

12. Example 2
If an image is measured and found to have a length of 6 mm (6,000 mm) and the magnification is 40,000 then:
Actual size of object = 6
40,000
= mm

13. Example 3
You have measured a chloroplast which is 30mm in length you have been told that the actual size is mm what is the magnification?
Divide 30 by
=60000
Magnification = x60000

14. The magnification can also be determined from scale lines drawn on images
length of scale line measured
length of scale line given
The scale line given on this
image has a value of mm
When this line is measured
with a ruler, it is found to
have a length of 30 mm
THEREFORE:
Magnification = 30
0.0005
= 6,000

15. of structures represented in the micrograph
The magnification value of x6,000 can be used to determine the actual dimensions
of structures represented in the micrograph
When the diameter of the red cell is measured with a ruler it is found to be 42 mm
The actual diameter of the
red blood cell is therefore:
size of image
magnification 42
6,000
= mm

16. Magnification Practice
The photograph below shows human cells as seen using a light microscope. It has been magnified 800 times.
(a) Calculate the actual diameter of the cell labelled A, expressing your answer in mm. Show your working.
Ms. Campbell measured cell A as being 20 mm

17. Magnification Practice
The photograph below-shows part of an animal cell, as seen using an electron microscope. The magnification is ×5000
Calculate the actual length of the structure labelled B in mm. Show your working.
Ms. Campbell measured B as being 25 mm

18. Magnification Calculations
Complete the half-sheet handout
Show all of your work
Once completed turn it in and begin coloring your “Size Matters” Sheet.