W9 Basics of Electron Microscopy

Question 1

definition of resolution

Answer 1

the smallest distance between two points that can be differentiated

human eye has resolution of about 0.1-0.2mm

Question 2

basic component of electron microscope

Answer 2

electron gun: produce electron beam

accelerator stack: provide strong voltage to equip electrons with very high speed

condenser lens system: to direct and focus the electron beam onto the sample

objective lens: produces a magnified real image of the sample and is used for focussing

projector lens: allow easier control of the magnification and projects magnified image onto a detector

Question 3

difference between TEM and SEM

Answer 3

TEM:
- detect electrons that are transmitted through sample
- internal structure observation
- passes through the sample
- 2D, high resolution
- thin samples

SEM:
- detect secondary electrons, backscattered
- surface structure observation
- scans the surface
- 3D like, detailed surface view
- bulk samples

Question 4

what is vitrified water

Answer 4

water that has been transformed into a glassy, solid state without forming any ice crystals

Question 5

how does x-ray crystallography work

Answer 5

sample is crystallised > shine x-ray onto crystal > bounce off into different directions that make a special pattern on detector > pattern used to determine exact shape of molecule