1. (Physiology) the faculty or sense by which sound is perceived. 2. an opportunity to be listened to. 3. (General Physics) the range within which sound can be heard; earshot. 4. (Law) the investigation of a matter by a court of law, esp the preliminary inquiry into an indictable crime by magistrates. 5.
The grey hair ârule of thumbâ is that by the age of 50, half of the population have lost the colour in 50% of their hair. When researchers tested this rule, they found that 74% of people aged between 45 and 65 had grey hair, with an average intensity of 27%. Generally, men have more grey hair than women.
Hair color is a matter of chemistry! The first safe commercial hair color was created in 1909 by French chemist Eugene Schuller, using the chemical paraphenylenediamine. Hair coloring is very popular today, with over 75% of women coloring their hair and a growing percentage of men following suit. How does hair color work? It's the result of a series of chemical reactions between the molecules in hair, pigments, as well as peroxide and ammonia if present. What is Hair?