2: Microscopy Flashcards
What are light microscopes
Light rays pass through specimen on a slide and are focused by an objective lens and an eyepiece lens. Produces magnified image on specimen on the retina of the eye.
Why use coloured stains on a light microscope
To make particular parts of the cell visible. Different stains are taken up but different parts of the cell.
What is an electron microscope
Uses beams of electrons rather than light rays. The specimen has to be very thin and must be placed in a vacuum to allow electrons to pass through it. Electrons are focused On the screen where they form a magnified image.
Why are heavy metals used for electron microscopy
Heavy metals such as gold don’t allow electrons to pass through them, so these can be used as stains to make particular parts of the specimen look darker than other
What is magnification
Size of image % actual size of the object
Can be rearranged to:
Actual size of object= size of image % magnification
What is resolution
The ability of the microscope to distinguish two objects as separate from one another. Small the objects that can be distinguished, the higher the resolution
What is resolution determined by
By the wavelengths if the rays that are being used to view the specimen. The wavelength of s even if electrons is much smaller objects than a light microscope. Therefore can see finer detail in electron microscope
What does 1 mm convert to in m
1x10 -3
What does 1um convert to m
1x10 -6
What does 1 nm convert to m
1x10 -9
What is a graticule
Eyepiece graticole is a little scale bar that you can place in the eyepiece of your light microscope. You can see the graticule as well as the specimen
What is calibration
When you covert to real units. You need a special slide called a stage micrometer thag is marked off in a tiny scale.
