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Micro_Ch 02
Microscope
| Question | Answer |
|---|---|
| What is the basic unit of length in the metric system? | The meter (m). |
| In what units are the sizes of bacteria and protozoa usually expressed? | Micrometers (µm). |
| How many micrometers (µm) and nanometers (nm) are contained in one meter? | 1,000,000 micrometers and 1,000,000,000 nanometers. |
| What is the nanometer equivalent of 1 micrometer (µm)? | 1,000 nm. |
| What is the micrometer equivalent of 1 nanometer (nm)? | 0.001 µm (or \(10^{-3}\) µm). |
| What is the typical size range of microorganisms featured in this chapter? | 1 µm to 200 nm. |
| What is the wavelength range of visible light? | Between about 380 nm and 730 nm. |
| What is the relationship between light wavelength, frequency, and energy? | The shorter the wavelength, the higher the frequency and energy. |
| What is a microscope? | An optical instrument used to observe tiny objects that cannot be seen with the unaided human eye. |
| What is resolution (resolving power)? | The ability of lenses to distinguish two points as separate entities. |
| What is the limit of resolution for the unaided human eye? | 0.2 micrometer (µm). |
| How does wavelength affect the resolving power of a microscope? | The shorter the wavelength, the greater the resolving power |
| How does the lens angle affect a microscope's ability to receive light? | The wider the angle of the lens, the greater its capability to receive light and the higher its resolving power. |
| What is refractive index? | The light-bending ability of a medium. |
| Why is immersion oil used in light microscopy? | To keep light from bending away from the high-magnification lens; it shares the same refractive index as glass. |
| What defines a simple microscope? | A microscope that contains only one magnifying lens (e.g., a magnifying glass). |
| What was the maximum magnifying power of Anton van Leeuwenhoek’s simple microscopes? | About 300X (300 times). |
| What defines a compound microscope? | A microscope that contains more than one magnifying lens |
| What is a photomicrograph? | A photograph taken through the lens system of a compound microscope. |
| What is the formula for calculating total magnification? | Total Magnification = Objective Lens × Ocular Lens |
| What is the maximum typical magnification and resolution limit of a compound light microscope? | 2,000X magnification with a resolution limit of 0.2 µm. |
| What are the key features of Brightfield Microscopy? | Objects are visible against a bright background; it is most commonly used to observe live or preserved stained specimens. |
| What are the key features of Darkfield Microscopy? | Objects are visible against a dark background because only light scattered by the specimen enters the objective; it is used to view outlines of live, unstained specimens. |
| Which type of microscope is classically used to observe the spiral bacterium Treponema pallidum? | Darkfield Microscope |
| What are the key features of Phase-Contrast Microscopy? | It accentuates the diffraction of light passing through a specimen to view internal cellular details of live, unstained specimens. |
| How does a Fluorescent Microscope make specimens glow? | A built-in ultraviolet (UV) light source strikes fluorescent dyes (fluorochromes), causing them to emit a longer, visible wavelength of light against a dark background. |
| What is Confocal Microscopy? | A technique that uses fluorochromes and a laser light to illuminate individual planes of a specimen, combining them to form a 3D image. |
| Why do electron microscopes have a much higher resolving power than light microscopes? | They use electrons instead of light, and the shorter wavelength of electrons yields significantly greater resolution. |
| What are the two primary types of electron microscopes? | Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). |
| What is a Transmission Electron Microscope (TEM) used for? | To fire an electron beam through an extremely thin specimen (<1 µm thick) to view internal cell structures. |
| What is the typical magnification and resolution limit of a TEM? | Up to 100,000X magnification with a resolution limit of 0.2 nm. |
| What is a Scanning Electron Microscope (SEM) used for? | To bounce electrons off the specimen's surface to create three-dimensional images of outer surfaces. |
| What is the maximum magnification and typical resolution limit of an SEM? | Up to 650,000X magnification with a resolution limit of 20 nm. |
| What color are raw scanning and transmission electron micrographs? | They are naturally black and white images. |
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