THE MICROSCOPE Flashcards
The ratio of the apparent size of an object as seen through the microscope & the
actual size of the object
Magnification
- The ability of the lens to clearly separate or distinguish two points of two lines
individually in the image. - It is determined by the shortest wavelength of visible light & maximum numerical
aperture
Resolution/Resolving Power
- A measurement of the ability of the condenser and the objective lens to gather light.
- Scanner : 4x : 0.10
- LPO : 10X : 0.25
- HPO : 40X : 0.65
- OIO : 100X : 1.25
. Numerical Aperture
- Thickness of the object that maybe seen at one time under focus.
- Distance between the center of a lens or curved mirror and its focus
Focal length
- Distance between the front lens of the objective lens & the top of the cover glass when the
specimen is in focus.
Working distance
- Refers to quality of the objectives & eyepiece where practically no change in focus has to be
made when objective is substituted for another
Parfocal
- Bending of light rays away from the objective lens when light passes from the glass of the microscope slide to the air.
Refractive Index
• First microscope.
• Created in the 17th century by Antony van Leeuwenhoek, who combined a convex lens with a holder for specimens.
• 200 – 300x Magnification
• Not used often today because the introduction of a second lens led to the more powerful compound microscope
Simple Microscope
• Two lenses
• Better magnification than a simple microscope
• Bright field microscopes (the specimen is lit from underneath, and they can be binocular or monocular) provide a magnification of 1,000 times, which is considered to be high, although the resolution is low.
• Allows users to take a close look at objects too small to be seen with the naked eye, including individual cells.
Compound Microscope
- Stained tissue is examined with ordinary light passing through the preparation.
- The microscope includes an optical system and mechanisms to move and focus the specimen
Bright field microscopes
- Tissue sections are usually irradiated with ultraviolet (UV) light and the emission is in the visible portion of the spectrum.
- Fluorescent substances appear bright on a dark background
Fluorescence Microscopy
- uses a lens system that produces visible images from transparent objects and, importantly, can be used with living, cultured cells
Phase-Contrast Microscopy
-Allows the recognition of stained or unstained structures made of highly organized subunits.
-Tissue structures containing oriented macromolecules are located between the two filters, they appear as bright structures against a dark background.
Polarizing Microscopy
• Uses electrons rather than light for image formation.
• Samples are scanned in vacuum or near vacuum conditions, so they must be specially prepared by first undergoing dehydration and then being coated with a thin layer of a conducive material, such as gold.
Scanning Electron Microscope (SEM)
• Uses electrons rather than light for image formation.
• Samples are scanned in vacuum or near vacuum conditions, so they must be specially prepared by first undergoing dehydration and then being coated with a thin layer of a conducive material, such as gold.
• After the item is prepared and placed in the chamber, the SEM produces a 3-D, black-and white image on a computer screen.
Scanning Electron Microscope (SEM)
-uses electrons in creating a magnified image
- Uses a slide preparation to obtain a 2-D view of specimens, so it’s more suited for viewing objects with some degree of transparency.
- Offers a high degree of both magnification and resolution
Transmission Electron Microscope (TEM)
used to support and adjust the parts
Mechanical Parts
used to enlarge the specimen
Magnifying Parts
used to provide light
Illuminating Parts
bottom post portion that supports the entire
microscope, provides stability and support for the
microscope when it is upright. The base also typically
holds the illuminator, or light source
• Base
part above the base that supports the other parts
Pillar
allows for tilting for the convenience of the user
Inclination joint
connects the eyepiece tube to the base ,curve or slanted part which is held while carrying the microscope
Arm
is a platform for the slides, which hold the specimen.
Stage and stage clip
attached to the arm and bears the lenses
Body tube
cylindrical structure on the top of the body tube that holds the ocular lenses
Draw tube
contains the objective lenses. Microscope users can rotate this part to switch between the objective lenses and adjust the magnification power
Revolving nosepiece
lies atop the nose piece and keeps dust from settling on the objectives
Dust shield
moves stage (or body tube) up and down, used to focus the image on the microscope under low or medium power
Coarse Adjustment Knob
small knob, used to focus of your specimen after using the coarse adjustment knob
Fine Adjustment Knob
contains the ocular lens, which the user looks through to see the magnified specimen, further magnify the image produced by the objective lenses by 5x
to 15x
Ocular/ Eyepiece
combine with the eyepiece lens to increase magnification levels. Microscopes generally feature three or four objective lenses, with magnification levels ranging 4x to 100x.
Objective lenses
microscopes require a light source for viewing. This can come in the form of a built in, low-voltage illuminator light, or a mirror that reflects an external light
source like sunlight
Illuminator or Electric Lamp
has a concave and plane surface to gather and direct light in order to illuminate the object
Mirror
focus the light onto the specimen, concentrating light rays on the specimen
Condenser
controls the amount of light reaching the specimen and regulates the light necessary to obtain a clear view of the object
Iris Diaphragm
