Magnification

Question 1

What is the magnification equation?

Answer 1

Magnification = size of drawing / true size of organism
M = I/A

Question 2

What units should you calculate magnification in?

Answer 2

Measure image in mm and convert to micrometers (x1000)

Question 3

How does a light microscope work?

Answer 3

Very thin samples used so that light can pass through and then be refocused by the condenser lens be observed

Question 4

What are the properties of light microscopes?

Answer 4

• dead or live samples used
• section view
• image can be viewed directly
• colour
• 2D

Question 5

What are the properties of transmission electron microscopes (TEM)?

Answer 5

• higher magnification and resolution
• dead samples only
• section view only
• image cannot be viewed directly
• samples must be coated by in chemicals or gold (very thin)
• B+W
• 2D
• must be in a vacuum

Question 6

How do electron microscopes work?

Answer 6

Electron beams pass through thin sample. Electrons pass through denser areas more easily - contrast

Question 7

What are the properties of scanning electron microscopes (SEM)?

Answer 7

• higher resolution and magnification
• dead specimens only
• external view only
• staining required (chemicals or gold)
• 3D view only
• b+w
• must be in vacuum

Question 8

Why is the resolution of electron microscopes higher than light microscopes?

Answer 8

The wavelength of electrons is shorter than light

Question 9

What is magnification and resolution and how are they different?

Answer 9

Magnification- how much bigger a sample appears under the microscope vs in real life
Resolution- the ability to distinguish between 2 points on an image (the amount of detail)

Question 10

Explain the use of a graticule

Answer 10

The eyepiece graticule can measure the size of objects. The scale is 10mm long and divided into 100subdivisions. Cannot be used to directly measure the object as each objective lense will measure to a different degree.
Objective lens measuring 40x will give 250μm per unit