Microscopes

Microscopes

Light Microscopy
I Compound (brightfield): used for seeing size and shape.
Ocular: remagnifies image formed by objectives
Bodytube: image travels up this
Arm
Objective: primary lens
Stage: holds specimen
Condenser: focuses light through specimen
Diaphragm: controls light entering condenser
Illuminator: light source
Base
Course and fine knobs: focusing
A. uses visible light as a source of illumination
B. cannot resolve less than 0.2 micrometers
C. used to observe various stained specimens

II Darkfield: for live organisms. On a dark background
A. uses a special condenser with an opaque disc
B. used to examine living organisms that are invisible otherwise, or don’t stain easily
C. used to detect Treponema pallidum (syphilis)

III Phase contrast:
A. uses a special condenser
B. no staining needed
C. detailed examination of internal structures in living organisms

IV DIC (differential interference contrast):
A. Like a phase contrast
B. internal organisms look 3D.
C. Used for live organisms.
V Fluorescence:
A. uses ultraviolet light
B. Mycobacterium tuberculosis appears bright yellow
C. Used for fluorescent-antibody technique
VI Confocal:
A. Uses laser light to illuminate one plane at a time
B. Used to obtain 3D images
VII Scanning Acoustic
A. Uses a sound wave
B. Used to examine living cells attached to another surface. (cancer cells, artery plaque, etc)


Electron Microscopy
I Transmission (TEM)
A. uses a beam of electrons
B. 2D
C. used to examine viruses or internal structures of thin sections of cells
D. 10,000 – 100, 000X
II Scanning (SEM)
A. uses a beam of electrons
B. appears 3D
C. to study the surface features of cells and viruses
Scanned Probe
I Scanning tunneling
A. uses a thin metal probe to scan specimen
B. Shows bumps and depressions of atoms
C. resolving power much greater than that of an electron microscope
D. Provides very detailed views of molecules inside cells