Imaging Flashcards
What determines colour of light
Wavelength
How to make invisible objects visible
Stain with dyes
Use phase altering properties of object to create contrast
Manipulating optical pathway of microscope
What determines brightness of light
Amplitude
What has caused a revival in microscopy
Better optics Computer interfacing User friendly Multi apps Molecular probes Genetic engineering
Purpose of objective lens
Critical for resolution
Focusing on image
What does PLAN on objective mean
Flat field - whole field is flat and in focus (no blurry edges)
What does apochromat mean
Lens is colour corrected so colours are transmitted accurately. (No chromatic aberration)
Higher NA equals
Better resolution
Why is thin cover glass better
Less refraction
Purpose of immersion lenses in microscopy
Reduce refraction improving resolution
What is the purpose of the condenser
Focuses light onto specimen
Fills objective lens with light (except in dark field)
What is Abbe’s Law
Minimum resolving distance (d) is related to wavelength of light divided by the numerical aperture, which is proportional to the angle of the light cone formed by a point on the object, to the objective
What is kohler illumination
Provides an evenly illuminated field of view whilst illuminating the specimen with a wide cone of light
How does kohler illumination work
Forms two conjugate planes of light:
One contains specimen image
Other the filament from the light
Why NB to have kohler illumination
Best for recording data
Best illumination, resolution
Standardized viewing and imaging conditions
Why don’t we visualize fresh tissue
Soft
Decays quickly
Can’t get thin enough samples
Living cells too thin to see when unstained
Methods of fixing tissue
Chemical - aldehydes, oxidizing agents, protein denaturation
Freezing (physical) - liquid nitrogen, propane
What molecule forms backbone of dyes
Benzene
How do dyes stain
Acid-base interactions
Permeability and displacement
Deposition, impregnation, precipitation
Chemical reaction with colourless dye to form colorful compound