Logarithmic Scale - Example Scales

Example Scales

On most logarithmic scales, small values (or ratios) of the underlying quantity correspond to negative values of the logarithmic measure. Well-known examples of such scales are:

• Richter magnitude scale and moment magnitude scale (MMS) for strength of earthquakes and movement in the earth.
• ban and deciban, for information or weight of evidence;
• bel and decibel and neper for acoustic power (loudness) and electric power;
• cent, minor second, major second, and octave for the relative pitch of notes in music;
• logit for odds in statistics;
• Palermo Technical Impact Hazard Scale;
• Logarithmic timeline;
• counting f-stops for ratios of photographic exposure;
• rating low probabilities by the number of 'nines' in the decimal expansion of the probability of their not happening: for example, a system which will fail with a probability of 10−5 is 99.999% reliable: "five nines".
• Entropy in thermodynamics.
• Information in information theory.
• Particle Size Distribution curves of soil

Some logarithmic scales were designed such that large values (or ratios) of the underlying quantity correspond to small values of the logarithmic measure. Examples of such scales are:

• pH for acidity and alkalinity;
• stellar magnitude scale for brightness of stars;
• Krumbein scale for particle size in geology.
• Absorbance of light by transparent samples.