Microscopy

Question 1

Compare electron microscopes and light microscopes

Answer 1

Light Microscope:
- cheaper
- requires a light source
-organism can be alive
Electron Microscope:
- higher magnification
- higher resolution
- 3D
- organisms dead
- expensive

Question 2

Calculate magnification

Answer 2

Magnification = image size / real size

Question 3

Explain the method for microscopy practical

Answer 3

1. Peel off an epidermal layer of the onion using forceps
2. Mount onto the microscope slide with a drop of water using a pipette, making sure the tissue lies flat
3. Add 2 drops of iodine solution to stain the cells
4. Place the cover slip on by first placing one edge down on the slide and slowly lowering the other side of the cover slip using forceps. Make sure no air bubbles are trapped
5. Remove any excess stain by soaking it with paper towels
6. Place the slide on the stage of the microscope
7. Turn the nosepiece to select a low power objective
8. Set up the microscope - don’t look into the eyepiece yet. Use the coarse adjustment knob to raise the stage until the cover slip just touches the objective.
9. Look into eyepiece and turn the coarse adjustment knob to move the stage away until the image comes into focus (doing this avoids breaking the slide)
10. Turn nosepiece to select a high power objective
11. Repeat same process as above and then look into the eyepiece and turn the fine adjustment knob until the image comes into focus
12. Make a labelled drawing of a few of the cells you can see, including any features
13. Repeat these steps using a prepared slide