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Microbiology
Exam 01 - Microscopy
| Question | Answer |
|---|---|
| What is the formula to calculate the Power of Magnification? | P(mag) = P(ocular) x P(objective) |
| For our microscopes in lab, what magnification do we set the ocular at? | 10x |
| What is oil-immersion magnification? | 100x |
| There are four objective lens in a light microscope, what are they? | 1. Red (5x) 2. Yellow (10x) 3. Blue (40x) 4. White/Oil immersion (100x) |
| What are the working distances for the 4 objective lens? | 1. Red - n/a 2. Yellow 4.4 mm 3. Blue 0.43 mm 4. White 0.22 mm |
| What are the numerical apertures of the 4 objective lens? | 1. Red - n/a 2. Yellow 0.25 3. Blue 0.65 4. White 1.25 |
| What is the definition of "resolution"? | measure of degree of sharpness, the minimal distance that 2 points can come together yet you can still distinguish them as 2 separate things |
| T/F Resolution is a complete separate parameter from magnification | TRUE |
| What is the formula of resolution also known as? | The Abbe Equation |
| What is the formula of resolution? | d(istance) = 0.5 X wavelength / NA (numerical aperture) |
| What is the formula for NA (numerical aperture)? | NA = n (index of refraction of medium) X sin(aperture angle) |
| What is the index of refraction (n) for oil and water? | 1.56 (oil) & 0.3 (water) |
| What exactly is NA (numerical aperture)? | a dimensionless number that characterizes the range of angles over which the system can accept or emit light |
| T/F An increase in magnification requires an increase in resolution | TRUE |
| What happens when you have a bigger angle? | Bigger the sin of the angle -> bigger the cone of light -> better the magnification |
| In order to get a very small distance (d), what must happen to NA? | NA needs to be big |
| What happens to NA when you increase the index of refraction "n"? | NA increases |
| When you increase NA, what happens to magnification? | It improves! |
| What are the main colors in wavelength? | R(ed) O(range) Y(ellow) G(reen) B(lue) I(ndigo) V(iolet) |
| Which color gives you the best resolution? | Violet (due to lowest wavelength) |
| Which color has the highest wavelength? | Red (750nm) |
| What is the wavelength of light produced by filter that we use for class? | 500nm (blue filter) |
| Which color has the lowest wavelength? | Violet (400nm) |
| What is the resolving power of the light microscope? | 200 nm or 0.2 micrometers - can't view live cells; don' get good magnification/resolution |
| What are the types of light microscopes? | 1. Brightfield 2. Darkfield 3. Phase-contrast 4. Differential interference contrast (DIC) 5. Fluorescence 6. Confocal 7. Two-photon 8. Scanning acoustic |
| Which light microscope is used in lab? | brightfield, darkfield |
| What is a brightfield light microscope used for? | 1. specimen looks dark in front of a bright background 2. resolution is better than dark field 3. can only view organisms as small as 0.2 micrometer 4. staining required |
| What is a darkfield light microscope used for? | 1. specimen looks bright in front of a dark background 2. condenser blocks light from entering objective lens, instead picks up light reflected by specimen. 3. better contrast than bright field. |
| What is a phase-contrast light microscope used for? | uses special condenser containing ring-shaped diaphragm, no staining required, to facilitate detailed examination of the internal structures of living specimens |
| What is a DIC light microscope used for? | 1. uses 2 beams of light separated by prisms 2. no staining required 3. provide 3-D images 4. specimen appears colored |
| What is a fluorescence light microscope used for? | uses ultraviolet or near-ultraviolet source of light, for fluorescent-antibody techniques (immunofluorescence) to rapidly detect and identify microbes or clinical specimens |
| What is a confocal light microscope used for? | uses single photon, obtain 2-d and 3-d images of cells for biomedical applications |
| What is a two-photon light microscope used for? | uses two photons, image living cells, up to depth of 1mm, reduce phototoxicity and observe cell activity in real time |
| What is a scanning acoustic light microscope used for? | uses sound wave, examine living cells attached to another surface (such as cancer cells, artery plaque and biofilms) |
| What are the types of electron microscopes? | Usually kills bacteria: 1. Transmission 2. Scanning |
| What is a scanning electron microscope used for? | 3-dimensional - use to study the surface features of cells and viruses 1000-10,000x |
| What is a transmission electron microscope used for? | examine viruses or the internal ultrastructure in thin sections of cells (10,000-100,000x) |
Created by:
lophung
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