Biology Chapter 3 Flashcards

Questions and Answers

What is the path of light through a compound light microscope?

Light source (illuminator); condenser; specimen; objective lens; ocular lens.

How is total magnification calculated?

The total magnification of an object is calculated by multiplying the magnification of the objective lens by the magnification of the ocular lens (objective lens x ocular lens).

What is the role of the condenser?

Focuses the light onto the specimen.

What is the role of the Iris Diaphragm?

Controls the amount of light reaching the specimen. Signup and view all the answers

What are the steps of the bacterial smear?

A thin film of material containing the microorganism is spread onto the slide. A Bunsen burner is then used to dry everything up. Stain is applied, then washed off with water. The slide is blotted with absorbent paper and is ready for examination. Signup and view all the answers

What is the function of a bacterial smear?

Before a microorganism can be stained it must be fixed (attached) to a microscope slide, which kills the microorganisms and fixes them to the slide while preserving their structure. Signup and view all the answers

Define Resolution.

The ability to distinguish two objects from each other in fine detail and structure. Signup and view all the answers

Define Magnification.

Simply how much an image is enlarged. Signup and view all the answers

Define numerical aperture.

The measure of its ability to gather light and resolve fine specimen detail at a fixed object's distance. Signup and view all the answers

What are the components of Phase Contrast Microscopy?

Specimen is illuminated by light passing through an annular diaphragm. Direct light rays travel a different path that are reflected or diffracted as they pass through the specimen. These two sets of rays are combined at the eye. Signup and view all the answers

What are the Dark Field Microscopy Characteristics?

Examines living organisms that are invisible to the ordinary light microscope and cannot be stained or distort the image. Signup and view all the answers

How does the dark field microscope work?

Uses a special condenser with an opaque disk that eliminates all light in the center of the beam. Only light from the specimen reaches the objective lens, making the specimen appear light against a dark background. Signup and view all the answers

How do we use Fluorescence Microscopy?

Specimens are first stained with fluorochromes and then viewed through a compound microscope using an ultraviolet light source. Signup and view all the answers

When do we use Fluorescence Microscopy?

Fluorescence microscopy is used primarily in diagnostic procedures called fluorescent-antibody (FA) technique or immunofluorescence. Signup and view all the answers

What are fluorophores/fluorochromes? And what is excitation and emission?

Fluorescence results from a process that occurs when certain molecules called fluorophores absorb light. As they decay from an excited state, they emit fluorescent light. Signup and view all the answers

Define the electron microscope.

Viruses and internal structures of cells are examined by this; beams of electrons are used instead of light. Signup and view all the answers

What are new components in the electron microscopy?

Electron microscopes use electromagnetic lenses to focus a beam of electrons onto a specimen, ensuring better resolution due to shorter wavelengths. Signup and view all the answers

Why does the electron microscope have higher resolution and magnification power than a light microscope?

The beams of electrons are stronger than light; electron waves travel in shorter lengths with an electron resolution power of 0.2 um, about 100,000x smaller than visible light wavelengths. Signup and view all the answers

Study Notes

Path of Light in a Compound Light Microscope

Light travels from the light source (illuminator) to the condenser, then to the specimen, through the objective lens, and finally reaches the ocular lens.

Total Magnification Calculation

Total magnification is found by multiplying the magnification of the objective lens by the magnification of the ocular lens (Objective Lens x Ocular Lens).

Role of the Condenser

The condenser's purpose is to focus light onto the specimen, enhancing image clarity.

Function of the Iris Diaphragm

It controls the amount of light that reaches the specimen, allowing for better visualization of details.

Steps of Preparing a Bacterial Smear

A thin film of the microorganism is spread on a slide.
The slide is dried using a Bunsen burner.
Stain is applied and then washed off with water.
The slide is blotted with absorbent paper and is ready for examination.

Function of a Bacterial Smear

Fixes microorganisms to the slide, simultaneously killing them and preserving their structure with minimal distortion.

Definition of Resolution

The ability to distinguish fine details and separate two objects from each other.

Definition of Magnification

Magnification refers to how much an image is enlarged.

Definition of Numerical Aperture

A measure of a microscope's ability to gather light and resolve fine specimen details.

Components of Phase Contrast Microscopy

Highlights internal structures of living cells using light that passes through an annular diaphragm.
Combines direct and diffracted light rays at the viewer's eye, with direct rays appearing red and reflected/diffracted rays appearing blue.

Characteristics of Dark Field Microscopy

Used to observe living organisms that are invisible with standard light microscopy.
Ideal for specimens that cannot be stained without distortion.

Working Principle of Dark Field Microscopy

Utilizes a special condenser with an opaque disk to block direct light, allowing only light scattered by the specimen to enter the objective lens.
The specimen appears bright against a dark background.

Use of Fluorescence Microscopy

Specimens are first stained with fluorochromes and then observed using ultraviolet light through a compound microscope.

Applications of Fluorescence Microscopy

Primarily used in diagnostic methods such as fluorescent-antibody (FA) technique or immunofluorescence.

Fluorophores and Excitation/Emission

Fluorophores (or fluorochromes) absorb light and become excited, then emit fluorescent light as they return to a lower energy state.

Definition of Electron Microscope

An electron microscope examines viruses and internal cell structures using beams of electrons instead of light.

Components of Electron Microscopy

Uses electromagnetic lenses to focus an electron beam on the specimen, with electrons traveling in waves providing better resolution due to their shorter wavelengths.

Higher Resolution and Magnification in Electron Microscopes

Electron beams possess higher energy and shorter wavelengths than visible light, yielding significantly improved resolution (0.2 micrometers, 100,000 times smaller than light wavelengths).

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Test your knowledge of key concepts from Biology Chapter 3 with these flashcards. Each card provides a question and a precise definition, covering important topics such as light path in microscopes and how to calculate total magnification. Perfect for students looking to reinforce their understanding.