Dark Field Microscope
The dark-field microscope focuses the light from the illuminator onto the top of
the specimen rather than from behind the specimen. The specimen absorbs some
light waves and reflects other light waves into the lens of the microscope. The
field of view remains dark while the specimen is illuminated, providing a stark
contrast between the field of view and the specimen.Phase-Contrast Microscope
The phase-contrast microscope bends light that passes through the specimen so
that it contrasts with the surrounding medium. Bending the light is called mov-
ing the light out of phase. Since the phase-contrast microscope compensates for
the refractive properties of the specimen, you don’t need to stain the specimen
to enhance the contrast of the specimen with the field of view. This microscope
is ideal for observing living microorganisms that are prepared in wet mounted
slides so you can study a living microorganism.(^58) CHAPTER 3 Observing Microorganisms
Type of
Microscope Features Best Used for
Bright-field
Dark-field
Phase-
contrast
Fluorescent
Transmission
electron
microscope
Scanning
electron
microscope
Uses visible light
Uses visible light with a that causes the
rays of light to reflect off the specimen
Uses a condenser that increases
differences in the refractive index of
structures within the specimen
Uses ultraviolet light to stimulate mole-
cules of the specimen to make it stand
out from its background
Uses electron beams and electro-
magnetic lenses to view thin slices
of cells
Uses electron beams and electro-
magnetic lenses
Observing dead stained spe-
cimens and living organ-
isms with natural color
Observing living
organisms
Observing internal
structures of specimens
Observing specimens or anti-
bodies in clinical studies
Observing exterior surfaces
and internal structures
Giving a three-dimensional
view of exterior surfaces
of cells
Table 3-3. Quick Guide to Microscopy