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9.18 Exam study 3
| Question | Answer |
|---|---|
| Wavelength | Length of light rays; Technically the distance from the crest or one wave to the crest of the next. |
| Area of electromagnetic spectrum that is used for light microscopy | |
| White light | Combination of all colors of visible light |
| Resolution | ability of an optical device to show two items as separate and discrete entities rather than a fuzzily overlapped image. |
| What length of waves produces the best resolution in light microscopes (longer or shorter) | Shorter. If light waves are too long then diffraction will occur and the image will be distorted. Light waves must be small enough to fit between two objects for them to be resolved. |
| Reflection | the bouncing of light off an object |
| Transmission | passage of light through an object |
| Absorption | process in which light rays are neither passed through nor reflected off an object, but are retained and either transformed to another form of energy or used in biological processes |
| Luminescence | Process in which absorbed light rays are reemitted at longer wavelengths. |
| What causes an object to fluoresce? | When light rays are striking an object |
| what causes an object to phosphorescent | object continues to emit light when rays no longer strike it. |
| Refraction | Bending of light as it passes from one medium into another medium of a different density |
| Index of refraction | Measure of the speed at which light passes through a material |
| Why do we use immersion oil | It replaces the air gap between an oil immersion lens and a glass slide. this prevents loss of light due to refraction. |
| Why us diffraction a problem in microscopy? | Because the lens acts as a aperture through which the light must pass. |
| What is the relationship between magnification and the size of a lens? | the higher the magnifying power of a lens, the smaller the lens must be; therefore, the greater the diffraction and blurring it causes |
| What is the total magnification of each objective of the light microscope? | |
| Compound microscope | light microscope with more than one lens |
| Parfocal | remaining in approximate focus when minor focus adjustments are made. |
| Brightfield illumination | Illumination produced by the passage of visible light through the condenser of a light microscope |
| Darkfield illumination | the light that is reflected from an object rather than passing through it, resulting in a bright image on a dark background |
| Phase-contrast microscopy? why is it used? | Uses visible light with a special condenser that accentuates differences in the refractive indes of viewed structures. changes in the speed of light are seen as different degrees of brightness |
| What type of light is used in fluorescence microscopy | Ultraviolet light |
| Fluorchrome | |
| EM (Electron microscope) | Microscope that uses a beam of electrons rather than a beam of light and electromagnets instead of glass lenses to produce an image. |
| What does the electron microscope use instead of light | Electromagnets |
| What are the two most common electron microscopes | Transmission and Scanning |
| What is TEM? What advantage does it have? | Tranmission electron microscope. Utilizes very thin sections of a specimen to reveal the internal structures of cells including microbes |
| What does SEM stand for? What information does it give? | Scan Electron Microscope: type of electron microscope used to study the surfaces of specimen Specimens coated with metal |
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ijuswannarn1
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