A logarithmic scale is a nonlinear scale used when there is a large range of quantities. Common uses include earthquake strength, sound loudness, light intensity, and pH of solutions. It is based on orders of magnitude, rather than a standard linear scale, so the value represented by each equidistant mark on the scale is the value at the previous mark multiplied by a constant. Logarithmic scales are also used in slide rules for multiplying or dividing numbers by adding or subtracting lengths on the scales. == Common usages == The following are examples of commonly used logarithmic scales, where...