Magnification: Viewing an image larger than it's actual size
Resolution:The ability to see two different points and distinguishing between them
The material that is put under the microscope is referred to as the object; the magnification of an abject is how many times bigger the image is when compared to the object.
Actual size = image size/magnification
Magnification = image size/actual size
Remember 1mm = 1000μm
To convert mm > μm you X by 1000 To convert μm > mm / by 1000
The light microscope
Use visible light and different lenses to magnify images.
You can only see larger organelles in a cell with a light microscope because of the limiting resolving power. The limitations are not due to the construction of the equiptment but the natrue of light itself. The wavelength of light is 500-650nm so anything smaller than this can't be see. The maximu magnification of a light microscope is x 1500.
- The scanning electron microscope is often used to magnify the surface features of an organism or a cell.
- The electron beam is produced in the same way as a TEM
- The electrons in the scanning beam cause secondary electrons to be emitted from the surface of the sample. then these are detected by a device which produces a signal that can be saved as a digital image.
The SEM can
- image a comparativley large area of the specimen.
- image bulk materials
The resolution of an SEM ranges from less than 1 nm to 20 nm depending on the instrument.
SEM images are generally easier to interpret than TEM images
- The transmission electron microscope reveals the detailed ultra-structure of plant and animal cells.
- very thin slices of specimen are cut preserved and stained. Then it is placed into the chamber inside the electron microscope.
- The air is sucked out to produce a vacuum.
- Electromagnets focus a beam of electrons that pass through the specimen and produce an image.