Studying Cells: Microscopes.. Magnification.. Flashcards
There are three key microscopes. What are three different types?
- Optical (light) microscope
- Transmission electron microscope
- Scanning electron microscope
Electron microscopes have two variations. What are two different types of electron microscopes?
Scanning electron microscopes and Transmission electron microscope
What is the definition of “magnification”?
The magnification of a microscope refers to how many times larger the image is compared to the object
What is the definition of “resolution”?
The resolution of a microscope is the minimum distance between two objects, whilst still being viewed as separate
How is the resolution in an optical microscope determined? How is the resolution in electron microscope be determined?
Optical microscope = wavelength of light
Electron microscope = wavelength of beam electrons
How do optical microscopes work?
The lenses focus rays of light and magnify the view of a thinly sliced specimen
Different structure absorb different amounts and wavelengths of light
Reflected light is transmitted to the overseer via the objective leans and eyepiece
What are the advantages of using an optical microscope? What are the limitations of using an optical microscope?
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Coloured images
Viewing live samples is possible
Affordable apparatus
- Has a lower magnification
Poor resolution due to microscope having longer wavelength, so ultrastructure cannot be seen
How does a transmission electron microscope work?
High energy beams of electrons pass through a thinly slice specimen
More dense structures appear darker because they absorb more electrons
Focus image onto photographic plate using magnetic lenses
How does an transmission electron microscope work?
High energy beams of electrons pass through a thinly slice specimen
More dense structures appear darker because they absorb more electrons
The image is then focused onto a photographic plate using magnetic lenses
What are the advantages of using a transmission electron microscope? What are the limitations of using an transmission electron microscope?
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Higher resolution power than optical microscope because of shorter wavelength making ultra structure visible
Higher magnification than optical microscope
- Produces only black and white images
Only non living samples as they must be in a vacuum
Extensive prep may introduce artefacts
How does a scanning electron microscope work?
A beam of electrons is focused onto a specimen using electromagnetic lenses
Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
What are the advantages of using a scanning electron microscope? What are the limitations of using an scanning electron microscope?
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Produces a 3D image
Electrons have shorter wavelength than light, causing high resolution
- No coloured images
Only shows outer surface
Requires a vacuum so cannot show living structures
Compare and contrast optical microscopes and electron microscopes (3pts)
Optical microscopes use beams of light to create their images, whereas electron microscopes use a beam of electrons to create their image.
Scanning electron microscopes can produced a 3D image whereas all optical microscopes can only produce
Electron microscopes produce blacks nd white images, whereas optical light microscopes produced images in colour.
What are the similarities and differences between scanning electron microscopes and transmission electron microscopes?
Scanning and transmission electron microscopes both produce black and white images
Scanning electron microscopes produces 3D images whereas transmission electron microscopes produce 2D images
Scanning electron microscopes do not require thin specimen samples whereas transmission electron microscopes need extremely thin and stained samples
Why can scanning electron microscopes use samples that are not thin?
Samples are not required to be thin because electrons are not being transmitted through
