2.3 More microscopy Flashcards
What are the 2 types of electron microscopes? Explain how each one works.
TEM - Beam of electrons is transmitted through a specimen and focused to produce an image. 0.5nm resolving power. Best resolution.
SEM - Beam of electrons is transmitted across surface of specimen and reflected electrons are collected. 3-10nm resolving power. Worse resolution but can produce 3D images.
Compare light microscopy with electron microscopy.
LM: Cheap to buy and operate
EM: Expensive to buy and operate
LM: Small and portable
EM: Large and requires installation
LM: Simple sample prep
EM: Complex sample prep
LM: Sample prep usually doesn’t lead to distortion
EM: Sample prep often distorts material
LM: Vaccuum not required
EM: Vaccuum required
LM: Produces natural sample colour
EM: Produces black and white images
LM: x2000 mag
EM: x500 000 mag
LM: 200nm resolving power
EM: TEM = 0.5nm RP. SEM = 3-10nm RP
LM: Specimens can be dead or alive
EM: Specimens must be dead
