The micrometre (International spelling as used by the International Bureau of Weights and Measures;[1] SI symbol: μm) or micrometer (American spelling), alsocommonly known as a micron, is an SI derived unit of length equaling 1×10−6 of ametre (SI standard prefix "micro-" = 10−6); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.000039 inch).[1] The symbol μm is sometimes rendered as um if the symbol μ cannot be used, or if the writer is not aware of the distinction.[citation needed]
The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria and is also commonly used in plastics manufacturing.[1] Micrometres are the standard for grading wool by the diameter of the fibres; wool finer than 25 μm can be used for garments, while coarser grades are used for outerwear, rugs, and carpets.[2] The width of a single human hair ranges from approximately 10 to 200 μm. The first and longest human chromosome is 10μm in length.
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[hide] 1Examples2SI standardization3Symbol4See also5Notes and references