Why does the x axis of a dose-response curve use log units?

Applying logarithm to the x axis of the dose response curve is a math trick that will linearize the middle zone of the curve and will allow you to visualize better  the  EC50 of the drug. Also the numbers on the x axis are easier to write since they are larger when you apply the logarithm to the concentrations.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.