Microscopy 2.1.1 (a,b,c,d,e,f) Flashcards
role of objective lens
produces a magnified image
role of eyepiece lens
further magnifies the image
structure of light microscope
what are the types of sample preparation?
dry mount
wet mount
squash slides
smear slides
what is a wet mount used for?
to observe aquatic samples
what is a wet mount?
the sample is suspended in a liquid and a cover slip is placed at an angle
what is a squash slide?
a wet mount is prepared and then the lens is used to squash the sample
what is a smear slide used for?
blood samples
what is differential staining?
used to differentiate between two types of organisms which are difficult to identify
examples of differential staining
gram stain
acid-fast
what is gram staining?
done to separate bacteria into two groups:
- gram positive
- gram negative
what colour are gram-positive bacteria when dyed?
crystal violet
what colour are gram-negative bacteria when dyed?
colourless
difference between gram-positive and gram-negative bacteria
gram-negative has thinner cell walls
what is magnification?
how many times larger an image is than the actual object viewed
what is resolution?
the ability to differentiate between individual objects as separate entities
why can electrons increase the resolution?
beams of electrons have wavelengths which are shorter than light
therefore they can be seen easier
equation for magnification?
magnification = image size / actual size
from mm to µm
x1000
from µm to nm
x 1000
from m to mm
x1000
what are two important components of a microscope for measurements?
an eyepiece graticule
a stage micrometer
what is an eyepiece graticule?
has a scale which is calibrated using a stage micrometer
allows you to measure image actual size
what is a stage micrometer used for?
to calibrate an eyepiece graticule
what is total magnification?
eyepiece lens magnification x objective lens magnification
what are the three types of microscopy?
light
electron
laser confocal
how is electron microscopy carried out?
a beam of electrons illuminates the sample
adv of electron
high magnifications
high resolution
disv of electron
expensive
hard to move
sample must be dead
black and white image produced
what are the two types of electron microscopy?
transmission electron microscope
scanning electron microscope
TEM vs SEM
has better resolution than SEM with 0.5 nm
produces 2D images
SEM vs TEM
has a lower resolution
produces 3D images
adv of light microscope
cheap to buy and operate
easy to move
easy to operate
can use alive samples
coloured image
disv of light microscope
weaker magnification and resolution
what is an artefact?
an object which is produced by the process of microscopy and can be seen under microscopy
what does laser confocal microscopy produce?
an image with a 3D structure from which different layers can be observed
