Microscopy

Question 1

What is the equation for magnification?

Answer 1

Magnification = image size/ actual size

Question 2

What is magnification?

Answer 2

• the degree to which the size of an image is larger than the object itself
• too high, can result in blurred image

Question 3

What is resolution?

Answer 3

• the ability to see two distinct points separately that are very close together
• increases the level of detail

Question 4

How do you calculate total magnification?

Answer 4

eyepiece x objective

Question 5

What is staining?

Answer 5

Using chemicals that react with other chemicals in the sample to…

Question 6

What is sectioning?

Answer 6

Using wax to stop the structure of the specimen from being distorted

Question 7

Describe an electron microscope:

Answer 7

• uses beam of electrons with a wavelength of 0.004nm
• resolution = 0.1nm (500,000x greater than human eye)
• uses magnets to focus
• creates an electron micrograph
• allows us to image viruses and DNA, which are smaller than 200nm

Question 8

What is an electron micrograph

Answer 8

an image on a screen or photographic paper created by an electron microscope

Question 9

Describe optical microscopes

Answer 9

• magnification: x1500
• resolution: 200nm
• method: light beams pass via object
• image type: 2D

Question 10

Describe SEM

Answer 10

• magnification = x100,000
• resolution = 1nm
• method: electron beam reflects off object’s surface; directed onto sample
• image type: 3D

Question 11

Describe TEM

Answer 11

• magnification: x500,000
• resolution: 0.05nm
• method: electron beam passes through sample
• image type: 2D (the darker the parts seen, the thicker the sample)

Question 12

Describe a TEM image

Answer 12

Slices through a plane of view which can be at any angle through any part of an organelle

Question 13

Pros of an optical microscope:

Answer 13

• can see colour
• easy to use
• accessible
• relatively cheap
• do not need a vacuum; can observe a living sample

Question 14

Cons of an optical microscope:

Answer 14

Low resolution and magnification; low retail

Question 15

Pros of an electron microscope:

Answer 15

electrons have a smaller wavelength (up to 100,000x) therefore there is a higher magnification and higher resolution

Question 16

Cons of an electron microscope

Answer 16

• cannot see colour
• requires skill and training to use
• inaccessible
• relatively expensive
• needs a vacuum- cannot observe a living sample
• requires greater preparation time (days)
• electrons can bounce off air

Question 17

How to use an electron microscope:

Answer 17

• fix the specimen
• dehydrate
• cut into thin slices
• stain
• mount onto copper grid
• place in vacuum in the microscope

Question 18

How do you calibrate the eyepiece graticule?

Answer 18

???

Question 19

Units

Answer 19

cm = 1/100th m
mm = 1/1000th m
μm = 1/1000000 m
nm = 1/1000000000 m