microscopy
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how does an optical microscope work?
light from a light source underneath the specimen passes through the specimen
what is the resolution of an optical microscope?
200nm
what is the magnification of an optical microscope?
x1500
what are the strengths of optical microscopes?
• colour image • uses live specimens
what are the weaknesses of optical microscopes?
• poor resolution • 2D image
what do optical microscopes allow us to see?
whole cells/tissues
how does a transmission electron microscope work?
electrons are transmitted through a specimen and denser parts of the specimen absorb more electrons, becoming darker
what is the resolution of a TEM?
0.5nm
what is the magnification of a TEM?
x1,000,000
what are the strengths of TEMs?
• good resolution
what are the weaknesses of TEMs?
• black and white image • 2D image • specimens must be dead
what do TEMs allow us to see?
small organelles
how do scanning electron microscopes work?
electron beam is scanned across the specimen surface and electrons bounce off, gathering in a cathode ray tube
what is the resolution of SEMs?
2nm
what is the magnification of SEMs?
x500,000
what are the strengths of SEMs?
• 3D image
what are the weaknesses of SEMs?
• black and white image • specimen must be dead
what is the magnification calculation?
mag = image / actual
what does magnification mean?
amount of times the image has been expanded than the object
what does resolution mean?
the ability to distinguish between two objects
which lens is the objective?
near to specimen
which lens is the eyepiece?
used to view specimen
why are there two lenses on a microscope?
• improves magnification • reduces chromatic aberration (diff colours travelling at diff speeds)
why is resolution limited for optical microscopes?
light has a larger wavelength