Questions and Answers
Robert Hooke published treatise 'Micrographia' using a simple ______.
microscope
The objective lens of a compound microscope projects a magnified image into the ______ tube.
body
Bright Field Microscope produces a dark image to a light ______.
background
Total magnification of a microscope is calculated by multiplying the eyepiece by the ______.
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Most commercial magnifiers produce a magnification of x2 to ______.
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The ______ lens magnifies the image formed by the objective lens.
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The ______ holds the objectives of the microscope.
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The distance between two front surfaces of the lens and the specimen is called the ______.
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The ______ controls the intensity of light produced.
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The ______ microscope does not allow light to pass directly through the specimen.
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The technique that uses fluorescent stains is known as ______ microscopy.
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An opaque disk with a thin transparent ring is called an ______ stop in phase-contrast microscopy.
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The numerical aperture (NA) describes the ______ gathering ability of the lens.
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The ______ microscope uses magnets to focus beams on the object being viewed.
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Ernst Abbe formulated the ______ sine equation.
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Study Notes
Microscopy Overview
- Robert Hooke published "Micrographia," a pioneering treatise on microscopy.
- Simple microscopes have a single bi-convex lens, primarily for dissection and observing bacterial colonies.
- Limitations of simple microscopes include low amplification (x2 to 30) and resolution (around 10 μm) due to low Numerical Aperture (NA).
Compound Microscope
- First developed by Zaccharias and Hans Janssen in 1590.
- Features two lenses: an objective lens near the specimen and an ocular lens near the eye, allowing for two-stage magnification.
- Significantly enhances viewing capabilities compared to simple microscopes.
Bright Field Microscope
- Produces dark images against a light background through visible light transmission.
- Total magnification calculated as eyepiece magnification multiplied by the objective’s power (e.g., 10x eyepiece and 100x objective yields 1000x).
- Key components include:
- Ocular Lens: Magnifies the objective's image.
- Body Tube: Transmits images to the ocular.
- Arm: Supports the microscope.
- Nosepiece: Holds objectives.
- Objective Lenses: Primary magnifying lenses.
- Mechanical Stage: Holds slides in place.
- Condenser: Focuses light on the specimen.
- Diaphragm & Rheostat: Control light intensity and amount.
- Adjustment Knobs: Coarse adjusts under low power; fine sharpens under all objectives.
- Illuminator: Provides necessary light.
Resolution and Numerical Aperture
- Resolution defined as the detail fidelity in magnified images.
- Ernst Abbe formulated the Abbe sine equation: d = 0.5λ/(n sin θ).
- Shorter wavelengths (450-500 nm) yield higher resolution, crucial for distinguishing close objects.
- NA indicates a lens's light-gathering ability; higher NA correlates to lower working distance.
Objective Lens Characteristics
- Scanning: 4x, NA 0.10, color red.
- Low Power Objective (LPO): 10x, NA 0.25, color yellow.
- High Power Objective (HPO): 40x, NA 0.65, color blue.
- Oil Immersion: 100x, NA 1.25, color white.
Dark Field Microscope
- Functions oppositely to bright field; light enters at oblique angles.
- Ideal for viewing spirochetes and other unstained microorganisms.
Phase-Contrast Microscope
- Designed for samples with low refractive indices, visualizing organelles without staining.
- Produces bright backgrounds with dark specimen images due to light beam deflection.
- Utilizes an annular stop condenser to create a hollow cone of light.
Fluorescence Microscope
- Employs fluorochromes that fluoresce under UV or visible light exposure.
- Common fluorochromes include acridine orange, auramine, and FITC.
- Converts radiant energy in molecules to fluorescence, used for detailed visualization.
Electron Microscope
- Utilizes electrons instead of light, capable of magnifying significantly smaller objects.
- Operates in a vacuum to prevent interference from air molecules.
- Produces an image via a monitor, allowing for high-resolution observation.
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Description
This quiz explores the fundamentals of microscopy, including the history and development of simple and compound microscopes. It also covers the principles of bright field microscopy, magnification calculations, and the key components involved. Test your knowledge on how these microscopes enhance our ability to observe microscopic specimens.
