Microscopy, Size & Magnification Flashcards
Parts of a Light Microscope
5 marks
- Eyepiece
- Objective Lens
- Stage
- Focusing Knob
- Light Source
Differences between Light Microscope and Electron Microscope: Light Microscope
(3 marks)
Light Microscope - shows details 0.2µm apart.
Needs a Magnification of x1500 so our eyes can see it.
Allows us to see larger cell structures.
Electron Microscopes
1 mark
Passes beams of electrons through a specimen
Differences between Light Microscope and Electron Microscope: Electron Microscope
(3 marks)
Electron Microscope - Greater resolution
Shows details 0.0001µm apart
Allows us to look inside the parts of a cell (inside chloroplasts/mitochondria)
How to look at Plant Cells through a microscope
4 marks
- Peel thin, transparent layer of epidermal cells from inside of an onion
- Place cells on (microscope) slide
- Add a drop of water/iodine
- Lower coverslip onto the cells using forceps or a mounted needle - gently to prevent trapping air bubbles
How to look at Animal Cells through a microscope
4 marks
- Remove cells from inside your cheek using a cotton bud
- Smear cotton bud onto a slide
- Add a drop of methylene blue (a Chemical Strain)
- Lower coverslip onto the cells using forceps or a mounted needle - gently to prevent trapping air bubbles
Lens can become damaged as it’s close to the slide
1 mark
High powered lens
Chemical Strains
1 mark
Used to make some cell parts more obvious.
Lower power objective lens
3 marks
- In a Compound Microscope
- Lens closest to specimen = short focal length and produces magnified image of specimen.
Objective Lens
3 marks
In a compound microscope - lens closest to the specimen
- has a short focal length and produces a magnified image of the specimen.
Field of View
1 mark
Area seen when looking through a microscope
Slide
2 marks
Thin piece of glass used to hold objects which are examined under a microscope
Resolution
1 mark
Ability to show detail.
Actual Length =
2 marks
Length of Image
_________________________________
Magnification
Magnification
(Equation)
(2 marks)
Size of Image
_____________________________________
Actual Size of Object
Magnification calculation
3 marks
- Measure scale bar image in mm
- Convert to µm (x1000)
- Magnification = scale bar image divided by actual scale bar length (written on the scale bar)
Total Magnification =
2 marks
Eyepiece Magnification
x
Objective Lens Magnification
Scale Bar
3 marks
- Line drawn near an image/drawing, labelled showing the actual length of the bar before magnified
- Magnification can be calculated using a scale bar
mm
1 mark
Millimetre
µm
1 mark
Micrometre
Convert mm to µm
(Convert Millimetres to Micrometres)
(1 mark)
x100
Multiply by 100
Once cells are in the middle of the field of view - you should?
(2 marks)
Rotate a higher powered lens into place
and begin to view the cells in more detail
Drawing Cell Structures
4 marks
Drawn in pencil - lines firm, continuous, no gaps
Large - Same proportions as the observed cell
Labelled - using separate ruled lines, spread out, bullet point one end and written label on the other
Title - includes its magnification or size
m
1 mark
Metre
Coverslip
2 marks
Small, square of glass placed on top of a specimen to prevent the cells drying out
- and to protect the microscope lens should it have contact with the slide.
Resolution: Detailed
3 marks
Fineness of detail that can be seen in an image -
Higher the resolution of an image = more detail it holds.
In computing terms, resolution is measured in dots per inch (dpi).
Epidermal
2 marks
Protective outer layer of skin
- in this investigation it is a single layer of cells found inside an onion.
