Module 2: Microscopy Flashcards
Convex lenses
Thicker in the centre
Light rays converge
Positive lenses
Concave lenses
Thinner in the centre
Light rays diverge
Negative lenses
Used to correct for aberrations
Focal length
Distance from the centre of the lens to the focal point
Working distance
Distance from the specimen to the objective lens
Depth of field
Range in which an object is in focus
Real image
Object is >1 focal length from lens
Image on opposite side of lens and can be focused on a screen
Inverted
Virtual image
Object within 1 focal length
Image on same side of lens
Magnified and erect
Must be viewed through a lens
Microscope component that magnifies the object and produces a real image
Objective lens
Microscope component that magnifies the real image
Ocular lens
Chromatic aberration occurs because
Shorter wavelengths are refracted more than longer wavelengths
Spherical aberration occurs because
Light passing through the centre of the lens does not bend as much as those passing through the periphery
Chromatic aberration causes
Distortion of colours
Spherical aberration causes
Blurry image
Three types of objectives with correction for chromatic aberration
Achromats, semi-apochromats, apochromats (best)
Lenses that are corrected for spherical aberration have the designation:
Plan