2.1 Microscopy

Question 1

What is resolution?

Answer 1

The smallest separation at which two separate objects/points can be distinguished

Question 2

What is the resolution of a microscope limited by?

Answer 2

The wavelength of light used

Question 3

How does a light microscope work?

Answer 3

• uses a series of lenses to produce an image that can be viewed directly at the eyepiece
• light passes from a bulb under the stage, through a condenser lense and then through the specimen.
• this beam of light is passed through an objective and then eyepiece lense

Question 4

Do light microscopes have high or low resolution?

Answer 4

Low

Question 5

What is the maximum resolution of s light microscope?

Answer 5

200nm

Question 6

What is the maximum magnification of a light microscope?

Answer 6

x1500

Question 7

What are the advantages of light microscopes?

Answer 7

• cheap
• portable
• you can stain the sample
• able to study living material

Question 8

What are the disadvantages of light microscopes?

Answer 8

• low resolution

- small cell organelle are not visible

Question 9

What is the staining technique?

Answer 9

Coloured stains bind to chemicals on or in the specimen allowing the specimen to be seen, due to increased contrast

Question 10

What is magnification?

Answer 10

How much bigger the image is compared to the original object

Question 11

What is sectioning?

Answer 11

• Specimens are embedded in wax

- thin sections are cut out without distorting the specimen

Question 12

What is sectioning useful for?

Answer 12

Making slides/sections of soft tissues such as brain

Question 13

What are laser scanning microscopes also called?

Answer 13

Confocal microscopes

Question 14

How do laser scanning microscopes work?

Answer 14

• use a laser to scan an object point by point
• can be used to view slices in the specimen without damaging it
• slices can be reformed into a 3D image

Question 15

What are advantages of laser scanning microscopes?

Answer 15

• high resolution and contrast
• can observe whole organisms and individual cells
• observe living and fixed specimens
• can focus structures at different depths of the specimen

Question 16

What are some disadvantages of laser scanning microscopes?

Answer 16

• lower resolution than electron microscope

- time consuming (sample is scanned point to point)

Question 17

How do you identify a laser scanning microscope image?

Answer 17

• fluorescence
• black background
• multiple layers

Question 18

What is a TEM?

Answer 18

Transmission electron microscope

Question 19

How does a TEM work?

Answer 19

Transmit a beam of electrons through a thin specimen and then focus the electrons to form an onscreen image

Question 20

What are the advantages of TEMs?

Answer 20

• highly detailed images of cells and organelles

- high resolution

Question 21

What are some disadvantages or TEMs?

Answer 21

• can’t study living material due to extensive preparation and vacuum
• expensive
• specific skill and training for sample preparation

Question 22

What is the maximum resolution of a TEM?

Answer 22

0.1 nm

Question 23

What is the maximum magnification of a TEM?

Answer 23

x500000

Question 24

What is a SEM?

Answer 24

Scanning electron microscope

Question 25

How does an SEM work?

Answer 25

By scanning a fine beam of electrons onto a specimen and collecting the electrons scattered by the surface

Question 26

What are advantages of SEMs?

Answer 26

- 3D images of cell surface - detailed - powerful magnification

Question 27

What are some disadvantages of SEMs?

Answer 27

- can't see inside cells - expensive - can't study living organisms - specific training for sample preparation

Question 28

What is the maximum magnification of an SEM?

Answer 28

x100000

Question 29

What is the maximum resolution of an SEM?

Answer 29

2nm

Question 30

What is the formula for calculating magnification?

Answer 30

Magnification= image size ➗ actual size

Question 31

What stain (chemical ) is used for staining plant cells?

Answer 31

Iodine

Question 32

What stain is commonly used for staining animal cells?

Answer 32

Methylene blue