A question on looking at a blood sample under a light microscope:
1. Make an estimate of the concentration of erythrocytes in this sample of blood. What facts do you need to produce this estimate? How accurately can you gauge each of these things? What do you judge to be the uncertainty in this estimate? How would you go about making a more accurate measurement and what additional apparatus would you need?
2. Could you use a sample of your own blood? What precautions would you need to take if you did?
Find out how.