Microscopes

Question 1

Define Magnification

Answer 1

The number of times bigger the image is compared to its actual size

Question 2

Define Resolution

Answer 2

The minimum distance between two points at which they can be seen as separate; the clarity of an image

Question 3

Why is the resolution lower on optical microscopes than on electronic microscopes?

Answer 3

Because light has a longer wavelength than electrons therefore the resolution is lower

Question 4

What is the magnification on both types of microscopes?

Answer 4

• Optical = x1,500
• Electron = x500,000

Question 5

What is the difference between a scanning and a transmission electronic microscope?

Answer 5

SEMs allow 3d images as electrons are reflected off of the surface of the cell
TEMs fire beams of electrons through the specimen allowing individual organelles to be seen

Question 6

What are the negatives of a SEM?

Answer 6

• Lower resolution than a TEM
• Only allows images of the surface of the specimen

Question 7

What are the negatives of electron microscopes?

Answer 7

• Specimens have to be cut thin
• Specimens must be in a vacuum which increases the risk of the cell hydrolysing (artefact images)
• Black and white images
• Complex preparation
• Expensive

Question 8

How do you use an eyepiece graticule?

Answer 8

Calibrate it with a stage micrometer of known length, and superimpose it over the specimen

Question 8

How do you use an eyepiece graticule?

Answer 8

First calibrate it with a stage micrometer of known length.