electron microscopes

Question 1

list the advantage of an electron microscope

Answer 1

+ electron beam has a short wavelength and therefore the microscope can resolve objects very well
+ as electrons are negatively charged the beam can be focused using electromagnet

Question 2

define TEM (in terms of what happens to produce an image)

Answer 2

(Transmission Electron Microscope)

electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet

Question 3

why do parts of the image appear dark during electron microscopy

Answer 3

the parts of the specimen that absorb electrons turn dark

Question 4

what are the limitations of electron microscopy

Answer 4

• the whole system is a vacuum therefore living organisms cannot be absorbed
• complex staining process is required
• image isn’t in colour
• specimen must be very thin
  (to produce a 2d image)
• image may contain artefacts

Question 5

define artefacts

Answer 5

things that are a result of the way specimen are prepared

Question 6

define SEM (in terms of what happens to produce an image)

Answer 6

directs a beam of electrons onto the surface of the specimen. The beam is passed back and forth across the specimen in a regular pattern.
(THIS PATTERN IS DETERMINED BY THE CONTOURS ON THE SPECIMENS SURFACE)

Question 7

list the advantages and disadvantages to an SEM

Answer 7

+ 3D images
+ higher resolving power than the light microscope