Microscopes

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22 Terms

1
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what is magnification?

how many times larger an object appears

2
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What is resolution?

the minimum distance between two distinct points where they can still be seen as separate objects

3
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on the stage micrometer 1 division

0.01 mm

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2 main microscopes

optical microscope and electron microscope

5
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electron microscopes types

  • transmission electron microscope (2d)

  • scanning electron (3d)

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in light microscopes, why can’t we see the organelles?

7
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max resolution and mag

200nm and mag is 1500x

8
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how electron microscope works - TEM

  • coats spectrum in resin to form solid block

  • thin slices are made, and stained with heavy metals

  • electrons pass thru the thin slice of material and are absorbed by the heavier stained metals. As they pass, they are photographed by electromagnets on the film.

9
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TEM captures . SEM captures _.

tem organelles. sem is whole cells, tissues, organisms

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scanning is about

how it’s reflected

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steps of how scanning electron microscope works

  • specium coated w/ thin layer of metal (like gold, tungsten, silver) to improve conductivity

  • electrons are reflected from the surface of specium, producing a 3D shape

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limits of electron microscope

complex, expensive, can’t look at living cells, ARTEFACTS can be made from preperation, black and white

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how to observe the cells in a prepared slide using light microscope

  • clip slide onto stage

  • select lowest powered objective lens

  • use course knob to bring stage just below objective lens

  • look down the eyepiece and use coarse knob to move stage down till image is roughly focused

  • adjust focus with fine knob till image is clear

  • if greater magnification is required refocus using a higher powered objective lens

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artefact

things that shouldn’t be there bc of staining in electron microscope

15
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Temporary mount

where the specimen is suspended in a drop liquid on the slide. the microscopy which Enchances colour of the spec

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Why is the resolution of Electron microscope higher than the resolution of a image using optical

electrons have much shorter wavelengths than photons (light particles), allowing them to resolve smaller details

17
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how to measure for size of a structure (real)

  1. measure image in mm and divide by mag

  2. convert image to micrometres

  3. divide image size by length of scale

  4. multiply real length of scale bar

18
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Why is it important for a leaf tissue to be very thin when observed

Thiness allows for light to pass thru specimun

19
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What are the measurement conversions needed for magnification?

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describe the steps to preparing a microscope slide using a temporary mount?

- begin by pipetting a small drop of water onto the centre of the slide.
2
- you will then need to place a thin section of your specimen on top of the water drop through using tweezers.
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- add a drop of stain. stains are used to highlight objects in a cell.
4
-add a cover slip.
-do this by standing the slide upright on the slide, next to the water droplet.
-carefully tilt and lower so specimen is covered.
-ensure no air bubbles are seen. they'll obstruct view of specimen.

21
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describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical light

  1. add a drop of water to glass slide

  2. obtain thin slice of plant tissue and place slice on drop pf water

  3. stain with iodine in potassium odiine

  4. lower cover slip using mounted needle

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