Microscopy Flashcards
How does a compound light microscope work?
The objective lens, which is placed near the specimen, produces a magnified image, which is then magnified again by the eyepiece lens, through which the specimen is viewed.
Sample preparation: Dry mount
Solid specimens are viewed whole or cut into very thin slices (sectioned). Eg hair, dust.
Sample preparation: Wet mount
Specimens are suspended in a liquid and a cover slip is placed on at an angle. Eg aquatic samples.
Sample preparation: Squash slides
A wet mount is first prepared, then a lens tissue is used to gently press down the cover slip. Eg root tip squashes to look at cell division.
Sample preparation: Smear slides
The edge of a slide is used to smear a thin and even layer of the specimen onto another slide. Eg blood.
Why are stains used?
Cell structures are often transparent, and stains increase contrast between structures as the different components take up stains at different degrees. This allows components to become visible and they can be identified
What is the definition of magnification?
Magnification is the amount of times larger the image is than the actual size of the object being viewed,
What is the definition of resolution?
Resolution is the ability to see individual objects as separate entities, or the amount of detail that can be seen.
How is magnification calculated?
Magnification = size of image/ actual size of object
Why do electron microscopes show more detail/ a higher resolution than light microscopes?
Electrons have a much smaller wavelength than light waves, so they can see more.
What image does a transmission electron microscope produce? (TEM)
A beam of electrons is transmitted through a specimen and focused to produce an image, similar to light microscopy. The inside of a cell is seen.
What image does a scanning electron microscope produce? (SEM)
A beam of electrons is sent across the surface of the specimen and the reflected electrons are collected. The surface of a cell is seen.
What is the definition of an artifact?
An artifact is a structure that is produced due to the preparation process, it is not a feature of the specimen.
What is the maximum magnification of a light microscope?
up to x2000
What is the maximum magnification of an electron microscope?
over x500 000
What is the resolving power of a light microscope?
200nm
What is the resolving power of an electron microscope?
TEM: 0.5nm
SEM: 3-10nm
