÷ Divide to make ____
bigger
Key Terms
÷ Divide to make ____
bigger
× Multiply to make _____
smaller
Describe how you convert cm → mm → μm → nm & vice versa
Define Magnification
How many times bigger the image is than the specimen (object)
Define Resolution
Minimum distance apart that two objects can be in order for them to appear as separate items
State the formula used to work out magnification
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| Term | Definition |
|---|---|
÷ Divide to make ____ | bigger |
× Multiply to make _____ | smaller |
Describe how you convert cm → mm → μm → nm & vice versa | |
Define Magnification | How many times bigger the image is than the specimen (object) |
Define Resolution | Minimum distance apart that two objects can be in order for them to appear as separate items |
State the formula used to work out magnification | |
Describe how optical (light) microscopes work | Light from bulb travels through condenser lens, then specimen, up through objective lens and through eyepiece lens into your eye |
State the maximum magnification for an optical microscope | x 1500 |
State the maximum resolution for an optical microscope | 0.2 µm |
Name 2 pros of optical (light) microscopes | Easy and cheap to operate Can have living specimens |
Name 2 cons of optical (light) microscopes | Low resolution & magnification Can’t see organelles smaller than 0.2 µm (e.g. ribosomes, endoplasmic reticulum and lysosomes) Specimens often need staining to show specific organelles |
Why does optical microscopes have a maximum resolution of 0.2 µm? | ∵ of the long wavelength of light rays |
Name 2 Electron Microscopes | Transmission Electron Microscopes Scanning Electron Microscopes |
Describe how transmission electron microscopes work | Use electromagnets to focus a beam of electrons which is then transmitted through the specimen Denser parts of specimen absorb more electrons = makes them look darker on image you end up with |
State the maximum resolution for a transmission electron microscope | 0.1 nm |
State the maximum magnification for a transmission electron microscope | x 10 000 000 |
Name a pro of transmission electron microscopes | Has highest resolutions & magnification See internal structure of organelles e.g. chloroplasts |
Name 4 cons of transmission electron microscopes | Non-living matter only Image in black and white and 2D Preparation may distort structure/give artefacts Vacuum required Elaborate preparation - staining is complex |
Describe how scanning electron microscopes work | They scan a beam of electrons across specimen = knocks off electrons from specimens Electrons gathered in cathode ray tube to form image |
State the maximum magnification of SEMs | x 30,000 |
State the maximum resolution of SEMs | 20 nm |
Name 3 pros of SEMs | Can form complex 3D images of sample Can be used on thick specimens Magnifications & resolutions are higher than light microscopes |
Name 3 cons of SEMs | Large and expensive & difficult to operate Specimens has to be mounted in vacuum Specimen has to be dead |
What type of cells are like algal cells? | Plant cells = have same organelles (Can be single-celled or multicellular) |
What type of cells are like fungal cells? | Plant cells |