MICROSCOPY Flashcards
What are the disadvantages of the scanning electron microscope? (3)
-samples have to be placed in a vacuum.
-very expensive.
-sample preparation complicated and expensive.
What are the advantages of the scanning electron microscope? (2)
-similar to electron microscope (magnification is only x100,000)
-produces 3D images that can show details of tissue arrangements.
How does a scanning electron microscope work? (2)
-3D samples are scanned, these samples are placed in a vacuum in specimen chamber.
-the microscope sends a beam of electrons that interacts with the surface of the specimens showing surface detail.
What are the limitations of the electron microscope? (3)
-samples have to be placed in a vacuum.
-very expensive.
-sample preparation complicated and expensive.
What are the advantages of the electron microscope? (2)
-high magnification.
-high resolution 0.2nm therefore see more detailed images and smaller specimens.
What is the magnification of an electron microscope? (1)
X500,000
What is an electron microscope? (3)
-electron beam passes through a very thin prepared sample.
-electrons pass through denser parts of sample less easily creating contrast.
-produces 2D images.
What is a light microscope? (1)
Uses light to view an object, also known as a compound microscope because each lens contains more than one glass lens.
What is thee function of the condenser lens? (1)
Focuses light before it hits the specimen to be viewed (near the base).
What is the function of the eyepiece lens? (1)
The one you look down.
What is the function of the coarse focus? (1)
The stage or the objective lens moves a greater distance than if you turn the fine-focus screw.
What is the function of the stage? (1)
Where you place the specimen to be viewed.
What is temporary preparation? (1)
Involves placing tissue on a glass slide, covering it with a water-based liquid to prevent it drying out and putting an extremely thin glass cover slip over it.
What is permanent preparation? (1)
The water has been removed from the tissue and been replaced by a finer substance, the cover slip is held in place by resin.
What is a stain? (1)
Used to help you see their structures.
What is the resolution of a light microscope? (1)
2 micrometers. (200nm)
What is the resolution oof an electron microscope? (1)
5nm.
What are the limitations of the light microscope? (2)
-most only magnify to a max of x1500
-maximum resolving power is 200nm, therefore detail is limited.
What are the advantages of a light microscope? (4)
-view a direct image.
-inexpensive and portable allowing wide use in education, lavatory analysis and research.
-food for viewing relatively large specimens.
-easy to prepare samples.
How does a light microscope work? (2)
-Light passes through the bulb under the stage and through the specimen more light passes through the less dense regions of the cell, creating contrast.
-the image is magnified by objective and eyepiece lenses.
Convert cm to mm and vice versa (2)
Cm to mm =x10
Mm to cm = /10
Convert mm to micrometer and vice versa (2)
Mm to micrometer= x1000
Micrometer to mm= /1000
Convert micrometer to nm and vice versa (2)
Micrometer to nm= x1000
Nm to micrometer= /1000
What is the formation for standard form? (1)
Nx10(n)
What is magnification? (1)
The degree to which the size of an image is larger than the image itself.
What is resolution? (1)
The degree to which its possible to distinguish between two objects that are very close together.
How do you calculate magnification? (1)
Magnification= image size/actual size
What stains ram positive bacteria, in terms of bacteriology? (1)
The cell wall becomes purple when stained by crystal purple.
What stands gram negative bacteria, in terms of bacteriology? (1)
The high lipid content of its outer membrane prevents the crystal violet stain getting to the cell wall, so the bacteria does not become purple, thus not staining.
How can you see the chromosomes of a cell, in terms of microscopy? (2)
-with a light microscope you can only see chromosomes when the nucleus divides.
-other times they appear dispersed as a diffuse network.
How can you see organelles like chromatin, chromosomes and the nucleolus, in terms of microscopy? (1)
Are only usable if stained with a certain dye.
What is a eye graticule? (1)
A small piece of glass with a measurement scale on its surface and fits inside a microscope eyepiece.
What is calibration? (1)
A comparison of the scale on the eyepiece reticle with the scale markings of a known dimension on a scale micrometer.
