(C) Microscopes Flashcards
Describe the principle of bright field microscopy.
White light passes through/reflects off of a specimen; differences in absorption of the light is due to different densities between various parts of the sample.
Illumination of bright field microscopy is from…
Tungsten filament or LED.
Describe the principle of Fluorescence microscopy.
Dyed specimen illuminated with short wavelength light (blue or ultraviolet light).
Special exciter filter allows only the shorter wavelength light to pass.
Fluorescent objects are bright against a dark background.
With Fluorescence microscopy, the filter absorbs blue light and emits longer ___ wavelength light.
yellow-green.
Describe the principle of Phase Contrast microscopy.
Hollow cone of light in the condenser plus absorption ring in objective produces a contrast.
Light slows down as it passes through specimen with rings which change the phase of light.
Phase Contrast microscopy is sensitive to differences in…
refractive index.
Phase Contrast microscopy is best used for what types of samples?
Unstained wet preparation.
Polarizing microscopy is used to examine…
Microorganisms that exhibit anisotropy or are birefringent.
Define Parfocal.
objects in focus with one objective only requiring minimal use of fine focusing to reestablish shart focus when rotation between objectives.
Define Parcentric.
Specimens centered in the field of view for one objective stay in the center when rotation between objectives.
What is an alternative cleaner that can be used to clean microscope objectives if lens cleaner is not available?
Methanol.
How should the condenser be positioned in stained slides?
All the way up.
