Microscopes 0.0 / 5 ? BiologymicroscopesASAQA Created by: charlie_hCreated on: 01-06-16 16:54 TEM - transmission electron microscope e~ beam is fired through the specimen, parts of specimen absorb e~ so appear darker than others and vice versa Image can be produced on screen and can be photographed to give a photomicrograph Resolving power of 0.1 nm however this cannot always be achieved because... difficulties preparing the specimen limit the resolution a higher energy e~ beam is needed which may destroy the specimen The main limitations of the TEM are... Whole system must be in a vacuum - so can't observe living specimens complex staining process is required - even then image not in colour specimen must be very thin image may contain artefacts (something that remains from staining process that is not acctually part of the specimen) image appears 2D unless multiple cross sections are taken to bulid up 3D image 1 of 4 SEM - scanning electron microscope Scans beam of e~ across the specimen and contour scatter the beam Produces 3D image Resolving power of 20 nm Limitations... Requires complex staining process Whole system must be in a vacuum - so cannot view living specimens Image may contain artefacts 2 of 4 Light microscope Can only distinguish between two points if they are 200nm or more apart - limited by the relativly long wavelength of light Can observe living specimens Cheaper Less complex staining methods 3 of 4 Unit conversions m to... mm X1000 um X1,000,000 nm X1,000,000,000 mm to... m /1000 um X1000 nm X1,000,000 um to... m /1,000,000 mm /1000 nm X1000 nm to... m /1,000,000,000 mm /1,000,000 um /1000 4 of 4
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