define magnification
how much bigger an object appears compared to the original
what magnification do microscopes produce
linear magnification
resolution
ability of an optical instrument to see/produce an image that shows fine detail clearly
why are optical microscopes good for schools to use
- cheap
- easy to use
- portable
- study whole living specimens
what type of light do optical microscopes (light) use
visible light
calculation for total magnification
total magnification = magnifying power of objective lens x magnifying power of eyepiece lens
photograph of image taken using an optical microscope (light)
photomicrograph
describe electron microscopes
- use beam of fast travelling electrons
- greater resolution
- give clear & highly magnified images
where are the electrons fired from in an electron microscope & how is a image created
- fired from cathode
- focused by magnets onto a screen or photographic plate
describe transmission electron microscopes
- specimin chemically fixed (dehydrated & stained)
- beam of electrons pass through specimen (stained with metal salts)
- form 2D black-and-white image
- very high magnification
what is the image formed by a transmission electron microscope called
electron micrograph
describe scanning electron miscroscopes
- secondary electrons to bounce off
- image focused onto screen
- 3D image
- high magnification
- black-and-white image (false colour can be added)
- specimen placed in vacuum & coated in fine metal film
magnification equation
image size divided by actual size
