world of microscope Flashcards
(23 cards)
how do light microscopes work
they use a beam of light to form an image of the object
what magnification can light microscopes achieve
2000x
advantages of light microscopes
-no radiation risk
-and are affordable
-With light microscopes large sub cellular structures can be seen
difference between light microscopes and electron microscopes
you can see live specimens on a light microscope but not an electron microscope as it uses a vacuum.
disadvantage of light microscope
-low magnification
-low resolution ( make it difficult to see smaller objects)
-Can only see the outside of the cells and nucleus
importance of the development of electron microscopes
it enabled scientists to see and understand more about the subcellular structures in cells
How do electron microscopes work?
they use a beam of electrons to form an image
What magnification can electron microscopes achieve?
up to x2,000,000
What do transmission electron microscopes do?
they give 2D images with high magnification and resolution
What advantages are there to using electron microscopes?
-higher magnification (up to x2,000,000)
-higher resolution
-Using a beam of electrons instead of a beam of light allows the electron microscope to gain a much higher resolution in seeing much smaller objects e.g. mitochondria, chloroplasts, ribosomes, plasmids
What disadvantages are there to using electron microscopes?
-they are large
-very expensive - 1million
- have to be kept in special temperature, pressure and humidity rooms
-Can only observe a dead specimen as it has to be observed in a vacuum and will die as there is no oxygen
How do you calculate magnification with a light microscope?
multiply the eyepiece lens by the magnification lens
-Total magnification = magnification of eyepiece (fixed 10x) x magnification of objective lens (4x, 10x, 14x)
How do you calculate size of a real object?
image size / magnification
what is resolution?
the ability of a microscope to distinguish details of a specimen or sample.
magnification
the increase in size of an object when it is viewed through a microscope or some other optical device
how to work out mean length of cells
-place ruler on stage
-measure diameter/ width of field of view in mm
-focus on cells
-estimate/ count number of cells that sit (lengthwise) across a field of view.
divide diameter/width of field of view by estimated number of cells
How do you calculate cell magnification from an image?
Magnification = Image Size/Actual Size
what are the two types of electron microscopes
-Scanning Electron Microscope (SEM)
electrons scan the surface of a sample
-Transmission Electron Microscope
electrons penetrate a sample - can see inside a sample
Explain how electron microscopy has increased understanding of sub-cellular structures:
-An electron microscope has a much higher magnification and resolving power
-This means it can be used to study cells in much more detail
-Scientists can now see (and better understand) sub-cellular structures
centimetres (cm) to millimetres (mm)
x10
millimetres (mm) to micrometres (µm)
x1000
micrometres (µm) to nanometres (nm)
x1000
What can be use to judge the relative size or area of sub-cellular structures?
-Scale bar: It’s a line or bar added to an image that shows how much distance in the image corresponds to a real-world length (like 1 μm, 500 nm, etc.).
-This helps you compare and measure the sizes of structures in micrographs (images from microscopes).
