Microscopy Flashcards
What is magnification?
-how many times larger the imagine is than the actual size
What is resolution?
-the ability to distinguish between 2 close together objects
What are optical microscopes?
-uses visible light
-limited by the wavelength of light
-specimen must be thin
What is the magnification and resolution of optical microscopes?
-M = x1500
-resolution = x200 nm
What are electron microscopes?
-exposes a specimen to electrons
-produces greater resolution images - as it has shorter wavelength than light
-observe small organelles
-2 types: TEM, SEM
What is the magnification and resolution of electron microscopes?
-M = x1,500,00
-R = 0.2 nm
What is a transmission electron microscope?
-uses electromagnets to focus beams of electron - transmitted through specimen
-denser parts absorb more electrons = darker
-high resolution
-only uses dead specimens, thin only
What is a scanning electron microscope?
-beam of electrons bounces off the surface
-electrons are detected = forming 3D image
-3D specimens external structure can be observed
-lower resolution, not coloured
What are laser scanning confocal microscopes?
-cells are stained with UV dyes - thick sections are scanned with laser beam
-beam is reflected by dyes
-multiple depths = whole image
-allows external structures to be observed
-slow process
What are the 4 types of mounts?
- Dry
- Wet
- Squash
- Smear
What are dry mounts?
-sectioned specimen - on slide - with cover slip
-eg, dust, muscle tissue or plants
What are wet mounts?
-suspended in a liquid
-cover slip at an angle
-eg. Aquatic samples
What are squash mounts?
-wet mount
-lens tissue presses down on cover slip
-eg. Root tips
What are smear mounts?
-edge of slide smears sample
-thin coating
-cover slip
-eg. Cells in blood
What does staining do in light microscopy?
-dyes absorb the specific colours while reflecting others
-certain tissue absorb certain dyes
-depending on chemical nature
