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)
