2.1.1 F) Difference between Magnification and Resolution

Question 1

Magnification

Answer 1

how enlarged the image is compared to the original object

Question 2

Resolution:

Answer 2

the ability of a microscope to distinguish between 2 separate adjacent points on an image as 2 separate objects

Question 3

Comparison of electron and light microscope magnification and resolution:

Answer 3

Magnification: light → LSCM → SEM → TEM

Resolution: light → LSCM → SEM → TEM

Question 4

How do light microscopes work?

Answer 4

use glass lens that focus a beam of light onto specimen on the slide (image produced is called a photomicrograph)

Question 5

When are light microscopes used?

Answer 5

used for visualising whole cells or tissues

Question 6

Magnification of light microscope:

Answer 6

2,000 x

Question 7

Resolution of light microscope:

Answer 7

0.2 µm

• not large enough to visualise any of the smaller organelles

Question 8

Advantages of light microscopes:

Answer 8

• can visualise living cells so we can watch behaviours such as cell division in real time
• cheaper
• portable
• images in colour
• require minimal training to use

Question 9

Disadvantages of light microscopes:

Answer 9

• lower magnification and lower resolution compared to electron microscopes - so produce less detailed images
• presence of light

Question 10

How does a TEM work?

Answer 10

• uses electromagnets to focus a beam of electrons at a specimen/sample
• which is then transmitted through the specimen to produce 2D images (electron micrograph)
• denser parts of the specimen absorb more electrons which makes them look darker on the image you end up with

Question 11

When are TEMs used?

Answer 11

to view thin specimens (tissue sections, molecules, etc) through which electrons can pass generating a projection image

Question 12

Magnification of TEM:

Answer 12

2,000,000x

Question 13

Resolution of TEM:

Answer 13

0.1 - 4 nm

Question 14

Advantages of TEM:

Answer 14

• electrons have much shorter wavelength compared to visible light which means higher resolution detailed images can be produced
• higher max magnification and max resolution than light microscope and SEM

Question 15

Disadvantages of TEM:

Answer 15

• sample needs to be fixed and placed in vacuum so cannot be used on living specimens
• very expensive
• large - not portable
• lack of availability - only found in specialised research facilities and hospitals
• training required to use
• metal stains used can be toxic/hazardous
• very large → not portable

Question 16

How does a scanning electron microscope work?

Answer 16

• emit beam of electrons towards a sample knocking electrons off specimen
• which are gathered in cathode ray tube and then used to form an image

Question 17

When are SEMs used?

Answer 17

in materials science for research, quality control and failure analysis

Question 18

Magnification of SEM:

Answer 18

500,000x

Question 19

Resolution of SEM:

Answer 19

10 nm

• lower resolution than TEMs

Question 20

Advantages of SEM:

Answer 20

• high magnification and high resolution (compared to light microscopes) so produce clearer images than light microscope
• can produce 3D images with depth of field
• can be used to look at the specimen at different depths so image not confused bu other components that are not in focus
• good for viewing surfaces

Question 21

Disadvantages of SEM:

Answer 21

• image is interpretation rather than real life image
• lower max resolution than TEMs
• lower max magnification than TEMs
• sample needs to be fixed and placed in vacuum so cannot be used on living specimens
• very expensive
• large - not portable
• lack of availability - only found in specialised research facilities and hospitals
• training required to use
• black and white (but artificial colouring can be added)

Question 22

How does a laser scanning confocal microscope work?

Answer 22

uses laser light to scan the slide point by point and assemble/compile one image using a computer

Question 23

When are LSCM’s used?

Answer 23

• used in medicine (for quick and effective diagnosis) and biological research
• not used much for magnitive powers

Question 24

Magnification of LSCM:

Answer 24

x17,820

Question 25

Resolution of LSCM:

Answer 25

800nm

Question 26

Advantages of LSCM:

Answer 26

• high resolution
• high contrast images - can see difference between tissues well
• have depth selectivity - so can be used for whole living specimens and cells and can make 3D images of cells
• suitable for viewing thick specimens

Question 27

Disadvantages of LSCM:

Answer 27

• much more expensive than normal light microscope
• lasers in older versions can damage cells
• formation of a “stack” of images can be time consuming as the microscope has to scan the image many times in layers
• slower imaging speed
• stain may need to be used
• high powered laser can damage eyes
• can be time-consuming
• lose perception of colour