microscopes

Question 1

Define resolution

Answer 1

• the clarity of an image: the higher the resolution, the clearer the image
• the ability to distinguish between 2 distinct point clearly

Question 2

Define magnification

Answer 2

The number of times larger an image appears, compared to the actual size of the object

Question 3

How does the light (optical) microscope work?

Answer 3

• use slight and several lenses in order to magnify a sample

- specimens are illuminated with light which is focused using glass lenses

Question 4

resolution of optical microscopes

Answer 4

0.2 micrometres

Question 5

magnification of optical microscopes

Answer 5

X1500

Question 6

Disadvantages if optical microscopes

Answer 6

• specimens have to be thin, small and transparent

- have a low resolution due to light

Question 7

Advantages if optical microscopes

Answer 7

• less expensive

- can examine living specimens

Question 8

How do scanning electron microscopes work?

Answer 8

• scan a beam of electrons across the specimen

- this knocks off electrons from the specimen which are gathered in a cathode ray tube to form an image

Question 9

resolution of SEM

Answer 9

0.002 micrometres

Question 10

magnification of SEM

Answer 10

less than X500,000

Question 11

Disadvantages of SEM

Answer 11

• lower resolution than TEM
• only shows the surface of cells
• specimens are dead as they must be viewed in a vacuum

Question 12

Advantages of SEM

Answer 12

produces a 3D image

Question 13

How do transmission electron microscopes work?

Answer 13

• use electromagnets to focus a beam of electrons which is then transmitted through a specimen

Question 14

resolution of TEM

Answer 14

0.0002 micrometres

Question 15

magnification of TEM

Answer 15

more than X1000,000

Question 16

Disadvantages of TEM

Answer 16

• only produce a 2D image
• only used on thin specimens
• angles at which specimen is cut can affect how they appear
• specimens have to be dead as viewed in a vacuum

Question 17

Advantages of TEM

Answer 17

• can look at small organelles

- has a high resolution

Question 18

How do confocal scanning microscopes work?

Answer 18

• use laser lights to scan an object point by point and assemble by computer, the pixel information into one image

Question 19

resolution of confocal microscopes

Answer 19

20 nanometres

Question 20

magnification of confocal microscopes

Answer 20

X1500

Question 21

Disadvantages of confocal microscopes

Answer 21

• big microscopes

- doesn’t always show a full sample

Question 22

Advantages of confocal microscopes

Answer 22

• builds a clean/clear 3D image

- can view specimens at different depths in thick specimens

Question 23

What is the function of the Iris Diaphragm?

Answer 23

it closes slightly to produce a narrow beam of light

Question 24

What is the function of objective lens?

Answer 24

collects light passing through the specimen and produces a magnified image

Question 25

What is the function of eye piece lens?

Answer 25

magnifies and focuses image from the objective lens into the eye-piece lens

Question 26

What is the function of the condenser lens?

Answer 26

focuses light onto the specimen held between the cover slip and the slide