Microscopes Flashcards
Cell theory? (3)
Both plant and animal tissue is composed of cells
Cells are a basic unit of all life
Cells only develop from existing cells
Magnification
How many times larger the image is when compared to the original object
Resolution ?
Ability to distinguish between 2 points
How can resolution be increased
Using beams of electrons which have a wavelength shorter than light - individual beams can be much closer before they overlap so objects which are smaller and closer can be seen seepedate
Diffraction
Waves spreading out as they pass close to structures
Light deflected from individual structures can overlap - detail lost
Optical microscopy structures that are closer than 1/2 wavelength of light cannot be seen separately
Magnification=
Side of image/ actual size of object
Light microscope
2 lenses - objective and eye piece
Objective lens produces a magnified image, magnified AGAIN b eyepiece
= chromatic aberration
Illumination from light underneath sample
Max mag and resolution of light microscope??
2000 and 200nm
4 types of preparation for light microscope
DRY mount
Wet mount - water or an immersion
Squash slides - wet mount, then lens tissue used to gently press cover slip down, damage avoided by squashing sample between 2 microscope slides
Smear slides - edge of slide used to smear sample
Electron microscopes
- beam of electrons with wave lens less than 1 NM
- more detail of cell ultra structure
- expensive
- specimen DEAD
- can get artifscts - structures produced due to preparation
Preparation of electron microscope slides
Stained with heavy electron dense element eg metal
Transmission electron microscope
2d image
0.2 nm
500,000 magnification
Scanning electron microscope
3D image
Resolution of 3-10nm
Reflected electrons are collected
Max mag =100,000
