Chapter 2: Microscopy
Type Lecture
Reviewed
Status Done
Light Microscopes
First microscopes invented and are still widely used
Microscopes enlarge the image of an
Resolution limit is 2 μm.
Unit Abbreviation Value
1 centimeter cm 10−2 meter or 0.4 inches
1 millimeter mm 10−3 meter
1 micrometer μm 10−6 meter
1 nanometer nm 10−9 meter
1 Angstrom Å 10−10 meter
Lenses Create Images by Bending Light
Light is refracted (bent) when passing from one medium to another.
Refractive index—A measure of how much a substance slows the velocity
of light.
Direction and magnitude of bending are determined by the refractive
indices of the two media forming the interface
Lenses
Focus light rays at a specific place called the focal point.
Distance between center of lens and focal point is the focal length.
Lens strength is related to focal length.
Short focal length = more magnification.
Chapter 2: Microscopy 1
, Light Microscope Varieties
Many varieties
Bright-field microscope
Dark-field microscope
Phase-contrast microscope
Fluorescence microscope
Confocal microscope
Compound microscopes
Two sets of lenses
The Bright-Field Microscope
Used to examine both stained and unstained specimens.
Produces a dark image against a brighter background.
Has several objective lenses producing different magnification.
Total magnification:
Product of ocular lenses and objective lenses
Better Microscope Resolution Means a Clearer
Image
Resolution - ability of a lens to distinguish objects from each other, rather
than a single larger object.
Wavelength of light used is major factor in resolution
Shorter wavelength = greater resolution
Working distance - distance between the front surface of lens and surface
of cover glass or specimen when it is in sharp focus.
Properties of objective lenses
Property Scanning Low Power High Power Oil Immersion
Magnification 4x 10x 40 to 45x 90 to 100x
Chapter 2: Microscopy 2
Type Lecture
Reviewed
Status Done
Light Microscopes
First microscopes invented and are still widely used
Microscopes enlarge the image of an
Resolution limit is 2 μm.
Unit Abbreviation Value
1 centimeter cm 10−2 meter or 0.4 inches
1 millimeter mm 10−3 meter
1 micrometer μm 10−6 meter
1 nanometer nm 10−9 meter
1 Angstrom Å 10−10 meter
Lenses Create Images by Bending Light
Light is refracted (bent) when passing from one medium to another.
Refractive index—A measure of how much a substance slows the velocity
of light.
Direction and magnitude of bending are determined by the refractive
indices of the two media forming the interface
Lenses
Focus light rays at a specific place called the focal point.
Distance between center of lens and focal point is the focal length.
Lens strength is related to focal length.
Short focal length = more magnification.
Chapter 2: Microscopy 1
, Light Microscope Varieties
Many varieties
Bright-field microscope
Dark-field microscope
Phase-contrast microscope
Fluorescence microscope
Confocal microscope
Compound microscopes
Two sets of lenses
The Bright-Field Microscope
Used to examine both stained and unstained specimens.
Produces a dark image against a brighter background.
Has several objective lenses producing different magnification.
Total magnification:
Product of ocular lenses and objective lenses
Better Microscope Resolution Means a Clearer
Image
Resolution - ability of a lens to distinguish objects from each other, rather
than a single larger object.
Wavelength of light used is major factor in resolution
Shorter wavelength = greater resolution
Working distance - distance between the front surface of lens and surface
of cover glass or specimen when it is in sharp focus.
Properties of objective lenses
Property Scanning Low Power High Power Oil Immersion
Magnification 4x 10x 40 to 45x 90 to 100x
Chapter 2: Microscopy 2
