Microscopes Flashcards
Define resolution.
Ability of a microscope to distinguish detail
Define magnification.
How much an image has been enlarged by
What is the formula for magnification?
Magnification = Image size/Actual size
How do we convert micrometres to millimetres?
μm to mm = divide by 1000
How do we convert from micrometres to nanometres?
μm to nm = x 1000
How do we convert from nanometres to picometres?
nm to pm = x 1000
What are the features of a light microscope?
- Uses visible light and two magnifying lenses
- Shallow depth of field
- must be focused exactly on the structure being observed - Maximum magnification = 1500
What are the different magnifying lenses of a light micrscope?
- Objective lens
2. Eyepiece lens
How do we calculate the total magnification of a light microscope?
Magnification of eyepiece x magnification of objective
What are the advantages of a light microscope?
- Portable
- Can observe dead, abiotic and live specimens
- Cheaper
What are the disadvantages of a light microscope?
- Cannot magnify as much as electron microscopes
- Low resolution: 200 nm
- Can’t operate in darkness
What are the features of an electron microscope?
- Uses beam of electrons focused by powerful magnet to produce an image
- Two types: Scanning and Transmission
What are the features of a scanning electron microscope?
- Uses beam to scan surface of specimen and generate electrons which are then collected by detector and processed by a computer
- Forms 3D image
- Large depth of field
- Maps surface of specimen
- Max magnification = 500,000
What are the features of a transmission electron microscope?
- Passes beam through the specimen
- Forms 2D image
- Maps cross-section of specimen
- Max magnification = 1,000,000
What are the advantages of an electron microscope?
- Much higher magnification and resolution
2. Produces high quality images
