microscopes

Question 1

name the two types of electron microscopes

Answer 1

transmission electron microscope (TEM)
scanning electron microscope (SEM)

Question 2

define magnification

Answer 2

the ratio of an objects image size to its real size.

Question 3

define resolution

Answer 3

the ability to distinguish between two points.

Question 4

list the limitations of using an electron microscope.

Answer 4

• tissues must be observed in a vacuum.
• living specimens cannot be observed, they must be dead.
• a complex staining process is required which may introduce artefacts into the image.
• specimens have to be very thin (for TEM)

Question 5

why must tissues be observed in a vacuum?

Answer 5

so that the electrons aren’t absorbed by molecules in the air.

Question 6

why does the specimen have to be very thin (TEM)?

Answer 6

so that electrons can pass through.

Question 7

why does the thickness of specimen not matter for SEMs?

Answer 7

because the electrons bounce off and don’t need to be passed through.

Question 8

what is the resolving power of TEMs?

Answer 8

0.1nm

Question 9

what is the resolving power of SEMs?

Answer 9

20nm

Question 10

what is an advantage of using transmission electron microscopes compared to using scanning electron microscopes?

Answer 10

transmission electron microscopes produce a 2D image which means the internal structures can be seen.

Question 11

what would significant detail not be seen using an optical microscope?

Answer 11

has a low resolution because light has a longer wavelength.