magnification Flashcards
what does magnification mean?
The degree to which the size of an image is larger than the object itself
what does resolution mean?
The degree to which it is possible to distinguish between two objects that are very close together.
The higher the resolution the greater detail you can see.
pros and cons of optical (light) microscope:
Pros: Relatively cheap, easy to use, portable, able to study living organisms.
Cons: Only able to see larger organelles within cells (i.e. not ribosomes/ER, diameter 20nm).
max mag and res of optical (light) microscope:
Max Magnification: x1500
Max Resolution: 200nm
optical (light) microscope:
• Staining of the specimen is required, beam is focused by condenser, objective and eyepiece lenses.
• Used to show biological activity Also, larger cellular structures
• Optical microscope slides can be used to view living organisms, smear of human
blood/cheek calls, and thins sections of animal/fungal/ plant tissue.
what is a A photograph of an image seen using an optical microscope called
Photomicrograph
Electron Microscopes:
Beam of electrons used to create the image, electrons are fired from the cathode and focused by magnets, rather than glass lenses. Fast-travelling electrons have a smaller wavelength than visible light. This accounts for the electron microscopes better resolution compared to optical microscope.
pros and cons of electron microscopes:
Pros: Can see smaller specimens due to higher magnification and in more detail due to higher resolution.
Cons: Extremely expensive, live specimens can’t be used by either, need lots of training to use.
When an image from an electron microscope is photographed it is called an electron micrograph.
two types of electron microscopes:
TEM and SEM
what is TEM
Transmission Electron Microscope (TEM):
what type of image does TEM create
2D black-and-white image created.
max mag and res of TEM
Max Magnification: x500,000
Max Resolution: 0.2nm
Transmission Electron Microscope (TEM):
• Image created by beam of electrons passing through specimen and being focused by electromagnet on photographic plate/ screen.
• Denser parts of the specimen absorb more electrons and look darker.
• Sample must be dehydrated (chemically fixed) and stained – so live specimens cannot be used.
• Used to view smaller organelles (e.g. Endoplasmic reticulum and ribosomes).
what is SEM
Scanning Electron microscope (SEM):
what type of image does SEM create
3D Image created (black-and-white but given false colouring by computer).
Max mag and res of SEM
Max Magnification: x100,000
Max Resolution: 10nm (some say 0.2)
Scanning Electron microscope (SEM):
• Electrons ‘bounce’ off the specimen’s surface and are focused onto a screen. Specimen is placed in a vacuum (so cannot be live) and is often coated with thin layer of metal.
Laser Scanning Confocal Microscopes:
• Use laser light (beam) to scan an object point by point to assemble a digital image (3D).
• High resolution and show high contrast
• Can be used to clearly observe whole living specimens, as well as cells.
• Used in medical profession (e.g. observing fugal corneal infection, faster more effective treatment).
• Specimens are stained with fluorescent dyes, which reflect the laser beams.
• Laser beam scanned at different depths: the laser beam can be focused at a specific depth
eliminating the blur of optical microscopes; or images can be taken at successive depths and fed into a computer to construct a 3D image. Can focus on structures of different depths – depth sensitivity.
𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 =
𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 = 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑜𝑏𝑗𝑒𝑐𝑡𝑖𝑣𝑒 𝑙𝑒𝑛𝑠 × 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑒𝑦𝑒𝑝𝑖𝑒𝑐𝑒 𝑙𝑒𝑛𝑠
(eyepiece x10, objective x40, total x400).
Magnification=
.
Image size / actual size
what is it called when an image from an electron microscope is photographed
it is called an electron micrograph.
