chapter_2 - Lenses and the Bending of Light Chapter 2 The...

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1 1 Chapter 2 The Study of Microbial Structure: Microscopy and Specimen Preparation 2 Lenses and the Bending of Light light is refracted (bent) when passing from one medium to another refractive index a measure of how greatly a substance slows the velocity of light direction and magnitude of bending is determined by the refractive indexes of the two media forming the interface 3 Lenses focus light rays at a specific place called the focal point distance between center of lens and focal point is the focal length strength of lens related to focal length short focal length more magnification 4 Figure 2.2
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2 5 The Light Microscope many types bright-field microscope dark-field microscope phase-contrast microscope fluorescence microscopes are compound microscopes image formed by action of 2 lenses 6 The Bright-Field Microscope produces a dark image against a brighter background has several objective lenses parfocal microscopes remain in focus when objectives are changed total magnification product of the magnifications of the ocular lens and the objective lens 7 Figure 2.3 8 Figure 2.4
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3 9 Microscope Resolution ability of a lens to separate or distinguish small objects that are close together wavelength of light used is major factor in resolution shorter wavelength greater resolution 10 •working distance — distance between the front surface of lens and surface of cover glass or specimen 11 Figure 2.5 12 Figure 2.6
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4 13 The Dark-Field Microscope produces a bright image of the
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This note was uploaded on 01/11/2009 for the course BISC 300 taught by Professor dr. d. w. smith during the Spring '07 term at University of Dundee.

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chapter_2 - Lenses and the Bending of Light Chapter 2 The...

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