Topic 2 -Microscopy Flashcards
List the metric (SI) units of measurement & abbreviations
10^-3 = 1mm 10^-6m = 1 micrometre (um thing) 10^-9 = 1nm (nano-metre)
conversion:
1000nm = 1um
0.001um = 1nm
What is absorption (light)?
light that is absorbed by an object, often results in heat
What is transmission (light)?
light that passes through an object
What is refraction (light)?
bending of light when it passes from one medium to another
What is reflection (light)?
immediate re-emission of light after it hits a mirrored surface. In microscopy results in reversal of light image
What is white light?
Many different wavelengths 400nm-700nm
What is fluorescence?
higher energy light hits a flurophore molecule which re-emits photons of lower energy
What is total magnification?
objective X ocular magnification
e.g. 4x objective, 10x ocular = 40x total
What is resolution?
ability of the lenses to distinguish two points
>200nm is maximum res. for light microscope
Explain how electron microscopy differs from light microscopy
A beam of electrons is used instead of light. Resolution is far greater.
Describe an acidic dye?
anionic, w/ negative charges on the chromophore (colour carrier)
Describe a basic dye?
cationic, w/ positive charges on the chromophore
Describe negative & positive staining
Positive = surface of microbes are negatively charged & attract basic dyes
Negative = microbes repel dye, dye stains background
A gram-positive stain is (colour)?
stained BLUE w/ crystal violet
A gram-negative stain is?
stained RED with safranin
