Chapter 0: Microscopy

Question 1

What are the two types of microscopes?

Answer 1

Electron Microscope and Light Microscope.

Question 2

Define: Magnification

Answer 2

Magnification: Is the number of times an image is greater than the actual image.

Question 3

Define: Resolution

Answer 3

Resolution: Is the ability to distinguish between two distinct objects.

Better resolution – Better clarity – Better detail

Question 4

What’s the equation for magnification?

Answer 4

Maginification=Image/Actual

Question 5

What are some of the differences between the light and the electron microscope?

1. Type of radiation/medium
2. Wavelength
3. Lenses
4. Maximum useful magnification
5. Best resolution
6. Image formed

Answer 5

Types of radiation​

1. Light: Light rays that travel through air
2. Electron: Electrons that travel through a vaccum.

Wavelength

1. Light: ​400-700nm (the visisble spectrum)
2. Electron: 0.005nm

Lenses

1. Light: Made of glass
2. Electron: Electromagnetic

Maximum useful magnification

1. Light: x1500
2. Electron: x500 000

Best resolution

1. Light: 200nm
2. Electron: 0.5nm

Image formed

1. Light: Colour
2. Electron: Monochrome

Question 6

What are the advantages of using an electron microscope?

Answer 6

1. High magnification
2. High resolution
3. SEM makes it possible to see 3D images
4. Not limited by visible spectrum

Question 7

What are the advantages of using a light microscope?

Answer 7

1. Cheap and easy to maintain
2. Don’t require a rigorous preparation routine
3. Don’t take up a lot of space
4. Produce coloured images
5. Can view living specimen

Question 8

Give reasons as to why the following stages of preparation are taken:

1. Fixation
2. Dehydration
3. Embedding

Answer 8

1. Maintains tissue in life-like state, stops decomposition
2. Removes water from tissue
3. Supports specimen for sectioning

Question 9

Why must the specimen be dehydrated in order to view in electron microscope?

Answer 9

Because water would vaporise in the vaccum (frying the specimen). Water would deflect electrons.

Question 10

Why are thinner sections used for electron microscope?

Answer 10

To allow electrons to pass through.

Question 11

How come we can view ribosomes with electron microscope?

Answer 11

Because electrons can have very short wavelengths, so that makes it useful to see small objects like ribosomes (80S/70S) unlike the light microscope which are limited by the wavelength of the visible spectrum.

Question 12

Why are specimens stained either with pigments/metal?

Answer 12

Makes specimen easier to see, contrast more visible and easier to see organelles. Metal absorbs electrons.