microscopy Flashcards
what is a hand lens?
used to magnify objects that are visible to the naked eye
what can you see with a hand lens?
- colour
- texture
- shape
- size
what hand lens be used for?
- finger print matching
- seed/insect identification
pros and cons of a hand lens?
\+ easy to use \+ good for small objects \+ portable and cheap - not practical and have to maintain the distance - field of vision is limited
what is magnification?
is how much bigger the image you see is than the actual specimen itself
what is resolution?
is how detailed an image is
- how well a microscope distinguished between two points that are close together
what is a light microscope?
is a tool that uses visible light to detect and magnify very small objects and enlarging them
pros and cons of light microscopes?
\+ greater resolution than hand lens \+ easy to use \+ small and portable \+ can observe living organisms - doesnt show any living internal structure - cannot show 3d images
what is the difference between magnification and resolution?
magnification is the ability to make small objects seem larger whereas resolution is the ability to distinguish two objects from each other
hazards of light microscopes?
- allow to cool before transporting/transmitting
- hold by the arm and under the base
what is the practical with the onoin?
- add a drop of water to the slide
- add a single layer of onion tissue to the slide
- add a drop of iodine to stain the cell components
- lower the cover slip at an angle, to avoid air bubbles
- draw an accurate observation and label key features
how do you draw observations?
- draw what you see under the microscope using a sharp pencil
- it is drawn clearly with unbroken lines
- no title, write magnification it was observed under
what is the formula for magnification?
magnification = image size/real size
what is scale bar length?
drawn length (um) x 500/ actual length (um)
what is an electron microscope?
uses a beam of electrons to magnify an objects image contain a vacuum as air particles would interfere with the beam
pros and cons of electron microscopes?
\+ higher range of magnification \+ higher resolution \+ clearer image - cannot work on live specimens - expensive and not portable - must have training to use - must have the right temp, pressure and humidity in the room
what are two types of electron microscopes?
transmission electron microscope (TEM)
scanning electron microscope (SEM)
what is TEM?
uses a beam of electrons which have a much shorter than light. TEM’s can magnify up to 500,00 times
pros and cons of TEM?
+ very high resolution
+ can see internal structures
- only used on thin specimens
- electrons transmitted through the specimen
what is SEM?
scans electrons over the surface of the specimen, so you can get a 3D image
pros and cons of SEM?
\+ can be used on thick specimens \+ can see images in 3d - lower resolution images - electrons bounced off the specimen - lower resolving power then TEM
what is the relationship between the field of view and magnification?
the higher the power of magnification, the smaller the field of view
