Microscopes

Question 1

How does a light microscope work?

Answer 1

Shines a light through the specimen, lenses magnify the image.
Often staining is used to highlight certain parts of the cell

Question 2

Pros and cons of light microscopes

Answer 2

PROS
Cheap
Small and portable
Can use live specimens+sample prep doesn’t usually lead to distortion of sample
Colour images

CONS
Low mag and res
2D

Question 3

What is the mag and res of a light microscope?

Answer 3

Mag= up to 2000x
Res=200nm

Question 4

How does an SEM work?

Answer 4

Fires a beam of electrons across specimen surface, the electrons rebound and detectors pick up electrons to make a 3D image

Specimen must be coated in metal and in a vacuum for this to work

Question 5

Pros and cons of an SEM

Answer 5

PROS
3D image
High res and mag

CONS
Specimen must be coated in metal and in a vacuum
Black and white image
Expensive
Hard to use
Dead specimen

Question 6

What is the mag and res of an SEM?

Answer 6

Mag= x100,000
Res= 3-10nm

Question 7

How does a TEM work?

Answer 7

Fires electrons through an ultra-thin section of specimen, dense areas absorb more electrons so make a darker image.

Specimen must be thinly sliced and embedded in resin

Question 8

Pros and cons of TEM

Answer 8

PROS
Highest mag and res

CONS
Black and white
2D
Sample must be dead and has a difficult specimen set up procedure

Question 9

What is the mag and res of a TEM?

Answer 9

Mag= 500,000x
Res=0.1-0.5