Biology AS CIE
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1-cell-structure10 主题
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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1-2-cells-as-the-basic-units-of-living-organisms AS prokaryotic-v-eukaryotic-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS the-vital-role-of-atp
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1-2-cells-as-the-basic-units-of-living-organisms AS animal-and-plant-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS eukaryotic-cell-structures-and-functions
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1-1-the-microscope-in-cell-studies AS calculating-actual-size
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1-1-the-microscope-in-cell-studies AS resolution-and-magnification
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1-1-the-microscope-in-cell-studies AS eyepiece-graticules-and-stage-micrometers
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1-1-the-microscope-in-cell-studies AS magnification-calculations
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1-1-the-microscope-in-cell-studies AS the-microscope-in-cell-studies
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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2-biological-molecules19 主题
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2-4-water AS water-and-the-hydrogen-bond
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2-4-water AS the-role-of-water-in-living-organisms
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2-3-proteins AS collagen
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2-3-proteins AS haemoglobin
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2-3-proteins AS globular-and-fibrous-proteins
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2-3-proteins AS protein-shape
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2-3-proteins AS the-four-levels-of-protein-structure
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2-3-proteins AS amino-acids-and-the-peptide-bond
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2-2-carbohydrates-and-lipids AS phospholipids
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2-2-carbohydrates-and-lipids AS triglycerides
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2-2-carbohydrates-and-lipids AS cellulose
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2-2-carbohydrates-and-lipids AS starch-and-glycogen
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2-2-carbohydrates-and-lipids AS the-glycosidic-bond
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2-2-carbohydrates-and-lipids AS reducing-and-non-reducing-sugars
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2-2-carbohydrates-and-lipids AS covalent-bonds-in-polymers
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2-2-carbohydrates-and-lipids AS biological-molecules-key-terms
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2-1-testing-for-biological-molecules AS testing-for-non-reducing-sugars
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2-1-testing-for-biological-molecules AS the-benedicts-test
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2-1-testing-for-biological-molecules AS biological-molecule-tests
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2-4-water AS water-and-the-hydrogen-bond
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3-enzymes13 主题
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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3-2-factors-that-affect-enzyme-action AS enzyme-inhibitors
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3-2-factors-that-affect-enzyme-action AS vmax-and-the-michaelis-menten-constant
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3-2-factors-that-affect-enzyme-action AS rate-inhibitor-concentration
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3-2-factors-that-affect-enzyme-action AS rate-substrate-concentration
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3-2-factors-that-affect-enzyme-action AS rate-enzyme-concentration
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3-2-factors-that-affect-enzyme-action AS rate-ph
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3-2-factors-that-affect-enzyme-action AS rate-temperature
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3-1-mode-of-action-of-enzymes AS colorimetry
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3-1-mode-of-action-of-enzymes AS measuring-enzyme-activity
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3-1-mode-of-action-of-enzymes AS how-enzymes-work
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3-1-mode-of-action-of-enzymes AS enzyme-action
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3-1-mode-of-action-of-enzymes AS enzymes
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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4-cell-membranes-and-transport16 主题
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-plant-cells
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4-2-movement-into-and-out-of-cells AS estimating-water-potential-in-plants
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4-2-movement-into-and-out-of-cells AS investigating-surface-area
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4-2-movement-into-and-out-of-cells AS surface-area-to-volume-ratios
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4-2-movement-into-and-out-of-cells AS investigating-diffusion
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4-2-movement-into-and-out-of-cells AS investigating-transport-processes-in-plants
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4-2-movement-into-and-out-of-cells AS endocytosis-and-exocytosis
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4-2-movement-into-and-out-of-cells AS active-transport
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4-2-movement-into-and-out-of-cells AS osmosis
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4-2-movement-into-and-out-of-cells AS diffusion
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4-1-fluid-mosaic-membranes AS cell-signalling
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4-1-fluid-mosaic-membranes AS the-cell-surface-membrane
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4-1-fluid-mosaic-membranes AS components-of-cell-surface-membranes
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4-1-fluid-mosaic-membranes AS the-fluid-mosaic-model
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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5-the-mitotic-cell-cycle8 主题
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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5-2-chromosome-behaviour-in-mitosis AS the-stages-of-mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS how-tumours-form
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-stem-cells
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-telomeres-
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5-1-replication-and-division-of-nuclei-and-cells AS the-cell-cycle
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5-1-replication-and-division-of-nuclei-and-cells AS mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS chromosome-structure
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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6-nucleic-acids-and-protein-synthesis9 主题
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6-2-protein-synthesis AS gene-mutations
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6-2-protein-synthesis AS transcription
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6-2-protein-synthesis AS constructing-polypeptides
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6-2-protein-synthesis AS the-universal-genetic-code
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6-2-protein-synthesis AS from-gene-to-polypeptide
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-rna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS semi-conservative-dna-replication
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-dna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS nucleotides
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6-2-protein-synthesis AS gene-mutations
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7-transport-in-plants11 主题
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7-2-transport-mechanisms AS phloem-mass-flow
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7-2-transport-mechanisms AS the-sucrose-loading-mechanism
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7-2-transport-mechanisms AS movement-in-the-phloem
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7-2-transport-mechanisms AS xerophytic-plant-leaf-adaptations
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7-2-transport-mechanisms AS water-and-the-transpiration-pull
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7-2-transport-mechanisms AS transpiration-in-plants
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7-2-transport-mechanisms AS water-and-mineral-ion-transport-in-plants
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7-1-structure-of-transport-tissues AS phloem-sieve-tube-elements
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7-1-structure-of-transport-tissues AS xylem-vessels-elements
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7-1-structure-of-transport-tissues AS xylem-and-phloem-distribution
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7-1-structure-of-transport-tissues AS plant-transverse-sections
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7-2-transport-mechanisms AS phloem-mass-flow
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8-transport-in-mammals16 主题
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8-3-the-heart AS heart-action
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8-3-the-heart AS the-cardiac-cycle
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8-3-the-heart AS the-walls-of-the-heart
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8-3-the-heart AS structure-of-the-heart
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-bohr-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-oxygen-dissociation-curve
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8-2-transport-of-oxygen-and-carbon-dioxide AS plasma-and-carbon-dioxide
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-chloride-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS red-blood-cells-haemoglobin-and-oxygen
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8-1-the-circulatory-system AS blood-tissue-fluid-and-lymph
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8-1-the-circulatory-system AS the-role-of-water-in-circulation
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8-1-the-circulatory-system AS cells-of-the-blood
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8-1-the-circulatory-system AS blood-vessels-structures-and-functions
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8-1-the-circulatory-system AS observing-and-drawing-blood-vessels
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8-1-the-circulatory-system AS the-main-blood-vessels
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8-1-the-circulatory-system AS circulatory-systems
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8-3-the-heart AS heart-action
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9-gas-exchange6 主题
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9-1-the-gas-exchange-system AS gas-exchange-processes
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9-1-the-gas-exchange-system AS structures-and-functions-of-the-gas-exchange-system
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9-1-the-gas-exchange-system AS recognising-structures
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9-1-the-gas-exchange-system AS recognising-tissues
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9-1-the-gas-exchange-system AS distribution-of-tissues
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9-1-the-gas-exchange-system AS the-human-gas-exchange-system
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9-1-the-gas-exchange-system AS gas-exchange-processes
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10-infectious-diseases6 主题
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11-immunity10 主题
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
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11-2-antibodies-and-vaccination AS how-vaccines-work
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11-2-antibodies-and-vaccination AS types-of-immunity
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11-2-antibodies-and-vaccination AS uses-of-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS making-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS antibodies
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11-1-the-immune-system AS memory-cells-and-immunity
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11-1-the-immune-system AS primary-immune-response
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11-1-the-immune-system AS antigens
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11-1-the-immune-system AS phagocytes
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
1-1-the-microscope-in-cell-studies AS eyepiece-graticules-and-stage-micrometers
Exam code:9700
Eyepiece graticules & stage micrometers
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An eyepiece graticule and stage micrometer are used to measure the size of an object when viewed under a microscope
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The eyepiece graticule is an engraved ruler that is visible when looking through the eyepiece of a microscope
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Eyepiece graticules are often divided into 100 smaller divisions known as graticule divisions, or eyepiece units
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The values of the divisions in an eyepiece graticule vary depending on the magnification used, so the graticule needs to be calibrated every time an object is viewed
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The calibration is done using a stage micrometer; this is a slide that contains a tiny ruler with an accurate known scale
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Stage micrometer rulers can vary, but often have larger divisions of 0.1 mm (100 μm) and smaller divisions of 0.01 mm (10 μm)
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Calibrating the eyepiece graticule
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In the diagram, two stage micrometer divisions of 0.1 mm, or 100 μm, are visible
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Each 100 µm division is equal to 40 eyepiece graticule divisions
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40 graticule divisions = 100 µm
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1 graticule division = number of µm ÷ number of graticule divisions
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1 graticule division = 100 ÷ 40 = 2.5 µm; this is the magnification factor
Calculating the size of a specimen
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The calibrated eyepiece graticule can be used to measure the length of an object
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The number of graticule divisions covered by an object need to be multiplied by the magnification factor:
Graticule divisions covered by object x magnification factor = length of object (µm)
Worked Example
A student viewed some onion cells under a microscope.
The image below shows the cells with an eyepiece graticule (left) and the eyepiece graticule alongside a stage micrometer (right).
Note that each large division on the stage micrometer here is 100 μm, and each small division is 10 μm.
Use the stage micrometer to calibrate the eyepiece graticule and calculate the actual length of the cell labelled C-D in the image.
Answer:
Step 1: Calculate the size of each eyepiece division
There are 40 graticule divisions per large micrometer division, or per 100 μm
1 graticule division = no. of μm ÷ no. of graticule divisions
= 100 ÷ 40
= 2.5 μm
This value can now be used as a magnification factor
Step 2: Calculate the length of the cell
Specimen size = no. of graticule divisions x magnification factor
The cell closest to the ruler covers 27 graticule divisions
= 27 x 2.5
= 67.5 μm
Step 3: Consider whether this answer makes sense in context
Plant cells usually measure between 10-100 μm, so a result of 67.5 μm sounds sensible in this context
Examiner Tips and Tricks
The calculations involving stage micrometers and eyepiece graticules are often seen in exam questions, so make sure that you are comfortable with how to calibrate the graticule and calculate the length of an object on the slide.
Note that both of the examples given above are carried out at the same magnification, so the magnification factor calculated during calibration is 2.5 in both cases. This may not always be the same in an exam.
Responses