Tools of Science The Microscope. An instrument that can form an enlarged image of an object. ...
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Transcript of Tools of Science The Microscope. An instrument that can form an enlarged image of an object. ...
Tools of ScienceThe Microscope
The Microscope
An instrument that can form an enlarged image of an object.
Visible light is passed through the specimen and through glass lenses. The lenses refract light to enlarge the image projected to the eye.
Schematic of Light Microscope
Properties of Microscopes
Magnification- how much larger compared to the real size The two lenses are the
ocular and objective lens. To determine magnification, multiply the magnifying power of the ocular by the magnifying power of the objective lens.
Properties of Microscopes
Resolving Power a. a measure of clarity
b. minimum distance between two points that can still be distinct as two points.
Limitation on Resolution
• Limit is .2 micrometers
• Limit is set by the wavelength of light (400-700nm or .4 micrometers)
Rayleigh Criterion
The Electron Microscope
• 1931 Ernst Ruska invented the electron microscope
• Beam of electrons focused by magnets.• Wavelength of a resonating electron is .004nm.
The resolution is limited by the ability to focus electrons with a magnet to approximately .2nm.
• The resolving power of the microscope is inversely related to the wavelength of electromagnetic radiation used.
• The specimen will be dead!!!
TEMTransmission electron microscope used to view internal structure.
200,000x
SEM-Scanning Electron Microscope
Surface sprayed with metallic mist.
Scans surface of objects with electrons.
Electrons bounce off of surface and are projected on a screen.
Image appears 3D. 100,000x magnification
of cell surface ultrastructure.
Schematic of SEM
Scanning Tunneling Microscope
• Specimen can be living!!!!
• 100 million x• Electrons tunnel off of
any surface and and electron gun measures the electron cloud thickness.
• Uses electrons that leak from the surface.
Confocal Microscopy