Questions and Answers
What part of the microscope is responsible for magnifying the image created by the objective?
The objective is the least complex part of the microscope.
False
What is the formula for calculating the total magnification of a microscope?
M = Mobj. x Meyep. x Kt
The ______ part of the microscope includes the illuminating source and condenser.
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Match the following parts of a microscope with their functions:
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Which component of the mechanical part is responsible for moving the stage?
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As the magnification of the objective increases, the working distance also increases.
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What happens if the eyepiece is removed from the microscope?
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What is the primary purpose of scanning electron microscopy (SEM)?
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Specimens for SEM are typically coated with a thick layer of resin.
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What technique is used in SEM to scan the sample surface?
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An image of a __________ can be produced by scanning electron microscopy to reveal fine surface details.
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Match the following items with their descriptions:
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What is the final magnification if the objective lens magnifies 100-fold and the eyepiece magnifies 10-fold?
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The numerical aperture (NA) is the same as the magnifying coefficient of the body tube.
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What does NA stand for in microscopy?
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The formula for numerical aperture is NA = n x sin(α). Here, n represents the __________ between the object and the objective.
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Match the following terms to their definitions:
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What happens to the resolution of a microscope as the numerical aperture (NA) increases?
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The minimum distance (d) between two distinguishable objects increases with a smaller numerical aperture.
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What does a larger value of α indicate in relation to the numerical aperture?
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In the formula d = λ/(NAobj + NAcon), λ represents the __________ of the light being used.
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What is the typical value of n for air in microscopy?
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What is the limit of resolution of a light microscope?
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The numerical aperture (NA) of an oil-immersion objective can only be 1.3.
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What is considered USEFUL MAGNIFICATION for a microscope?
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The formula for numerical aperture (NA) for a dry objective is NA = n x sin ______.
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Match the objective type with its numerical aperture range:
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What is the total magnification when using a 45x objective and a 20x eyepiece?
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EMPTY MAGNIFICATION occurs when total magnification is within the range of 500 to 1000 times NAobj.
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What is the maximum NA for a dry objective?
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If the total magnification is greater than 1000 x NAobj., it is termed ______ magnification.
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What is the sin value for the maximum angle of a dry objective?
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What happens when an objective of 45x is used with an eyepiece of 20x?
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The total magnification of 10x eyepiece combined with 45x objective is considered empty magnification.
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What do fluorescent molecules do in immunofluorescence microscopy?
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The two commonly used fluorescent dyes in immunofluorescence microscopy are __________ and __________.
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Match the following components of an electron microscope with their functions:
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Which of the following statements about electron microscopes is true?
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Immunofluorescence microscopy can detect specific proteins in tissues.
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What is the principal function of a transmission electron microscope (TEM)?
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The __________ filters the light before it reaches the specimen in a fluorescence microscope.
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Which of the following is NOT a feature of the fluorescence microscope?
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Study Notes
Main Parts of a Light Microscope
- Divided into three major components: Mechanical Part, Optical Part, and Illuminating Part.
Mechanical Part
- Includes the stand, arm, head (body tube), microscope screws (micro and macro), and stage.
- Revolving nosepiece holds the objectives; allows for quick rotation between different objectives.
- Stage adjustments are facilitated by screws for precise movement.
Optical Part
- Comprised of the eyepiece (ocular lens) and objective lenses.
- Objective lenses are crucial for image detail and quality.
Illuminating Part
- Contains the light source and condenser, which focuses light onto the specimen.
Function of Objective and Eyepiece
- Objective: The primary lens that creates the image, highlighting details.
- Eyepiece: Magnifies the image further, enabling visibility for the human eye. Its removal prevents any visibility of the specimen.
Working Distance
- The distance at which the objective lens can focus, measured from the cover slip to the lens.
- Higher magnification objectives have shorter working distances.
Total Magnification of Microscope
- Calculated as ( M = M_{obj} \times M_{eyep} \times K_t ).
- Individual lens magnification products yield total magnification. For example, a 100x objective and 10x eyepiece result in 1000x total magnification.
Numerical Aperture (NA)
- Formula: ( NA = n \times \sin \alpha ), where ( n ) is the refractive index and ( \alpha ) is the half-angle of the light cone.
- A higher NA value enhances resolution quality in microscopy.
Power of Resolution (d)
- Defines the ability to differentiate closely positioned objects.
- Calculated as ( d = \frac{\lambda}{NA_{obj} + NA_{con}} ); lower values indicate better resolution.
- The limit of resolution for light microscopes is approximately 0.2 μm.
Objectives
- Dry Objective: Uses air as the medium, with a maximum NA of 1.
- Oil-Immersion Objective: Uses immersion oil (n=1.5), improving resolution with an NA range of 1.3 to 1.5.
- Useful magnification lies between the range of ( 500 \times NA_{obj} ) and ( 1000 \times NA_{obj} ).
Immunofluorescence Microscope
- Uses fluorescent molecules to detect specific proteins or molecules in cells.
- Two filter sets manage illumination and emissions specific to fluorescent dyes like fluorescein (green) and rhodamine (red).
Electron Microscope
- Uses a beam of electrons as the source of illumination, requiring a vacuum for operation.
- Provides significantly higher resolving power and magnifications, up to 2 million times.
Types of Electron Microscopes
- Transmission Electron Microscopy (TEM): Similar to light microscopy, sends electrons through thin specimens.
- Scanning Electron Microscopy (SEM): Provides 3D surface images by scanning the specimen's surface with electrons.
Usefulness of Data
- Understanding the constraints of magnification and resolution is crucial when selecting objectives and eyepieces for specific microscopy applications.
- Accurate calculation of useful magnification is vital for effective microscopy, avoiding empty magnification that fails to provide additional detail.
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Description
Test your knowledge about the main parts of a light microscope, including the mechanical, optical, and illuminating components. Understand the functions of the objective and eyepiece, as well as the significance of working distance. Perfect for biology students and enthusiasts.
