THE COMPOUND MICROSCOPE Flashcards
There are two general categories of microscopes:
light microscope and the electron type
which uses light
waves and lenses that are associated with the _____ microscope,
light microscope
which employs electron beams and magnetic fields to produce the image.
electron type
Light microscopes can be classified as simple if they have short ______, are held close to the eye and magnify objects only up to ______X.
focal length,
300X
On the other hand, the compound type
employs two separate lenses, an ___ and an ________, in order to achieve ____ times greater
magnification.
ocular, objective
2-5
Other types of microscopes include (5)
bright field
dark-field
ultraviolet (UV)
fluorescent
phase-contrast
type of microscope where the microscope field is brightly lighted and the object to be observed appears dark die to its ability to absorb or refract some of the incident light
bright field microscope
type of microscope where the object appears luminous against a dark background since it reflects some of the incident light in all directions
dark-field microscope
type of microscope which uses UV light, thereby allowing greater resolution and magnification. It is used principally to detect or even measure substances in
specimens of living tissues that are known to absorb UV light at particular wavelengths. UV is not visible to the eye, so the image formed is recorded with the use of cameras or a television screen.
Ultraviolet (UV) microscope
type of microscope which makes use of the property of certain chemical substances that release light at a different wavelength when exposed to UV rays. Such substances convert UV light into visible waves of greater length. Bacteria and other microorganisms are stained with fluorescent stain that can be detected in a microscope illuminated with UV light.
Fluorescent microscope
type of microscope which utilizes the refraction that occurs when light passes from one medium into another of different density. The special objectives and condenser intensify slight differences in contrast produced by this bending of
light. It is useful in studying the internal structures of microorganisms because
structures differing in refractive index from the surrounding protoplasm become
visible, and their sizes and locations can be determined.
Phase-contrast microscope
keeps the microscope steady at any position of the stage
base
fastened to the base through the inclination joint, permits the adjustment of the stage to
a desired angle.
arm
reflects the light into the condenser.
concave mirror
concentrates the light rays received from the mirror and sends them to the objective
condenser
is a horizontal platform upon which the specimen to be examined is placed.
stage
At the center of the stage is a
circular aperture.
hold the slide in place on the stage.
stage clips
is that part of the optical system of the microscope which produces the specimen’s
initial magnified image (real) within the body tube.
objective
The student microscope has three objectives:
a dry low power, a dry high power, and an oil
immersion objective.
The objectives are ________, that is, they are corrected for the spectral colors of red and blue.
achromatic
Important features of the objectives: (4)
a. Focal length
b. Resolving power
c. Numerical aperture (N.A.)
d. Parfocal
an optical constant of the lens system, is the distance from the center of the lens to the point where parallel rays entering the lens are brought to a focus.
Focal length (mm),
of an objective is that property to recognize features of a specimen that are close to each other as separate or distinct.
The greater the _____, the greater the definition of an objective.
is dependent on the wavelength of light used and an optical property of the objective lens known as a numerical aperture.
Resolving power
