Magnification Flashcards
What do you need to do to see organelles in cells
You need to stain the cells
How does a light microscope work
A specimen is placed in a beam of light
The beam passes through a specimen and then through a series of lenses magnifying the image
In order for light to pass through what does the specimen need to be
The specimen needs to be thin and transparent
What are the 4 different slide types
Dry mount, Wet mount, Squash slides, Smear slides
What is dry mount
Dry mount - solid specimens are cut into very thin slices with a sharp blade (sectioning). The specimen is placed in the centre of the slide and a cover slip is placed on top.
What is wet mount
Specimens are suspended in a liquid such as water or an immersion oil. It is put on a slide and a cover slip is placed on from an angle.
What is a squash slide
A wet mount is prepared, and a lens tissue is used to press down on the cover slip.
What is a smear slide
The edge if a slide is used to smear the sample creating a thin even coating on another slide.
What does the eyepiece lens do
Magnifies and focuses the image from the objective lens onto the eye
What does the objective lens do
Collects light passing through the specimen and produces a magnified image
What is a condenser lens
Focuses the light onto the specimen between the cover slip and slide
What is a condenser iris diaphragm
Closed slightly to produce a narrow beam of light
What is the typical power of objective lenses
4x, 10x, 40x
What is low power
The lowest power objective lens
What is low power
The lowest power objective lens
Magnification definition
A measure of how much the image is enlarged relative to the specimen size
Resolution definition
the ability to distinguish between 2 points
What is the formula for maximum resolution
1/2 x wavelength
What is magnification
Size of image/size of object
What is an electron microscope
Uses a beam of electrons and not light, so has a lower wavelength and higher resolution
What is a TEM
Stands for a transmission electron microscope
What happens in a TEM
An electromagnetic coil focuses electrons onto a specimen and onto a screen or photographic plate for viewing.
What is the resolution and magnification of a light microscope
200nm (resolution), x1500-2000
What is the resolution and magnification of a TEM
0.2-0.5nm, x500,000 - 2,000,000
What is a SEM
A scanning electron microscope
What happens in a scanning electron microscope
Electromagnetic coils are used to scan the surface of a specimen with electrons, specimens are coated with gold and silver. Reflected electrons are collected and focused onto a viewing screen or camera.
Why must both electron microscopes be done in a vacuum
Air particles SCATTER electrons so it must be done in a vacuum. More dense objects scatter more electrons than less dense objects.
What is a graticle
Is a fixed scale inside an eyepiece. The divisions can be used to measure a magnified image, but you need to calibrate it.
What is a stage micrometer
It’s a 10mm scale etched into a slide with subdivisions of 0.1mm.
How do u use a stage micrometer and graticle
We place the stage onto the stage under low power so you can see the graticle and stage micrometer. You then find the number of eyepiece graticle units to stage micrometer units.
How do you measure specimens
You find the number of units in 1 eyepiece graticle unit and then multiply by the number of eyepiece graticle units in the specimens length or width.
What are the advantages of using a light microscope
inexpensive to buy and operate
Small and portable
simple sample preparation
Sample preparation doesn’t usually lead to distortion
Vacuum is not required
Natural colour of sample is seen
Specimens can be living or dead
What are the benefits of electron microscopes
Magnification and resolution
What is the resolution and magnification of a SEM
3-10nm and x100,000 - 500,000
