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lab5spr08handout - LAB 5 SPR `08 VIRTUAL PRACTICE IN USE OF...

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LAB 5 SPR ‘08 VIRTUAL PRACTICE IN USE OF THE BRIGHTFIELD MICROSCOPE http://www.udel.edu/Biology/ ketcham/microscope/scope.html Turn on sound. VIRTUAL PRACTICE IN KOHLER ILLUMINATION:. http://www.microscopyu.com/tutorials/java/kohl er/index.html VIRTUAL PRACTICE IN CALIBRATING AN OCULAR MICROMETER: http://www.microscopyu.com/tutorials/java/reticlecalibration/index.html THEORY OF MICROSCOPY The electromagnetic spectrum includes, in order of decreasing energy: x-rays, ultraviolet light, visible light (violet, blue, green, yellow, orange, red), radio waves, and heat. All electromagnetic radiation has the same speed in a vacuum, c, and oscillates in a periodic fashion. The speed of light is equal to the frequency of that oscillation (v) times its wavelength ( ). Higher-energy radiation has a higher frequency and correspondingly lower wavelength. http://www.olympusmicro.com/primer/java/electromagnetic/index.html The refractive index of a medium is a measure of how fast light can move through it. Light moves fastest through a vacuum, and then through air, and more slowly through increasingly dense substances such as glass. When light strikes an object of different refractive index straight on, it continues moving straight. However, when it strikes an object of different refractive index from an angle, it bends. The greater the refractive index of a substance, the more it slows down and bends light that enters it at an angle through air. http://www.olympusmicro.com/primer/java/refraction/refractionangles/index.html The bending of light by curved glass lenses is used to form magnified images in light microscopy. The lens through which light passes immediately after passing through the in a compound microscope is called the objective. Light traveling through the object is focused by the objective to form a real, inverted, magnified
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image. The eyepiece (ocular) lens forms an even more magnified image that is virtual and appears as though it were around the base of the microscope. The total magnification equals the magnification of the objective times that of the ocular. Magnification beyond a certain point is called empty magnification as it gives no more useful information. http://www.microscopy.fsu.edu/primer/anatomy/magnification.html The better the resolution of an objective, the more magnification can reveal additional information. Good resolution means two points can be separated from one another even if they are separated by a very small distance (d). Best resolution is achieved by an objective that can accept a wide cone of light. That is because the light rays hold information, and some of them are lost by an objective that accepts only a narrow cone of light. The cone of light accepted by a lens is determined by its numerical aperture.
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