2.2 magnification and callibration

Question 1

Magnification def and formula

Answer 1

How much bigger an image appears compared to the original object
calculated using the following formula:

mag= size of image/ actual size

Question 2

Resolution

Answer 2

The ability to distinguish two different points in a specimen. (lower res= detail is lost as structures overlap)

Question 3

How can we increase resolution

Answer 3

using wavelengths shorter than those of light eg beams of electrons

Question 4

Nanometers(nm) -> micrometers (um)->milimiters(mm)->meters(m)

Answer 4

divide by 1000

Question 5

what are the two types of electron microscopy

Answer 5

• transmission electron microscope TEM
• Scanning electron microscope SEM

Question 6

Transmission electron microscopes, ranking? how does it work?

Answer 6

highest resolution (lowest resolving power) highest magnification
beam of electrons transmitted through specimens similar to light microscopy 2D images. Denser parts absorb more so appear darker. Con: need a very thin specimen

Question 7

Scanning electron microscope SEM

Answer 7

lower res than TEM (higher resolving power) lower magnification than TEM
beams of electrons are refelcted across surface and then collected. 3D images

Question 8

electron vs light microscopy

Answer 8

Light:
cheaper to operate and buy
small and portable
sample prepe has minimal distortion
Colour
specimen can be alive
Electron:
more skilled and expensive
large and installed
sample prep often distorts specimen
B and W but can add colour digitally
specimen is dead

Question 9

Artefacts

Answer 9

visible structural detail caused by specimen preparation eg air bubbles

Question 10

Laser scanning confocal microscope

Answer 10

Uses laser beams to scan a specimen tagged with fluorescent dyes that give of light that’s focused onto the detector which feeds back to a computer to generate a 3D clear image of an alive specimen

Question 11

define sectioning in terms of microscopy

Answer 11

specimens are dehydrated with alchol the placed in a mould with wax or resi to form a hard block that can then be thinley sliced with a nife called a microtome

Question 12

define fixing in terms of microscopy preparations

Answer 12

chemicals like formaldhyde are used to preserve specimens in as near natural state as possible