The concentration of potassium ions is 5 mM outside and 100 mM inside, but the membrane is impermeable to these ions. We will keep the intracellular and extracellular fluids electroneutral by making sure that there's an appropriate number of matching negative ions (depicted as ‘A-’ above) on both sides of the membrane. If we measure Em in this new situation, it will be:
0 mV.
positive.
negative.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

the electromagnetic energy from the sun arrives in the form of visible and invisible light.

d. groundwater flows through the subsoil and deposits minerals.