Unit of length · BEGINNER LESSON
Micrometre
A micrometre is a metric unit of length equal to 10^-6 meter, written µm. It is also called a micron, and it is useful for describing very small sizes such as details seen in a microscope.
What it is
A micrometre is a unit used to measure length, not mass or time. Its symbol is µm, and it means 10^-6 meter, or one millionth of a meter. The same unit is also called a micron. In the metric system, this size is convenient when objects are too small for meters but still need a standard length value. [0][2]
[1] 1.2 Physical Quantities and Units - College Physics 2e | OpenStax [3] NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically
How it fits into measurement
The meter is the SI unit of length. SI means International System of Units, the worldwide standard system used in science. The meter is defined through the speed of light in vacuum, so the micrometre inherits that exact relation because it is simply a decimal fraction of the meter. The prefix micro- means 10^-6, while nano- means 10^-9; that makes a micrometre 1,000 nanometers. [1][0]
[2] www.nist.gov · pml · special-publication-330SP 330 - Section 2 | NIST [1] 1.2 Physical Quantities and Units - College Physics 2e | OpenStax
Where it is useful
Micrometres are practical when describing very small lengths, including details in microscopy. OpenStax lists micrometres among the metric prefixes used for tiny scales, alongside nanometres for even smaller measurements. A micrometre gives a more readable number than writing many decimal places in meters. [0]
[1] 1.2 Physical Quantities and Units - College Physics 2e | OpenStax
Limits and measurement meaning
A unit name does not by itself tell you how a value was obtained. The sources explain the micrometre as a derived decimal unit from the meter, and the meter itself has a defined physical basis through light in vacuum. In practice, the accuracy of any micrometre measurement depends on the instrument and method used to realize the meter and its subdivisions. [1][0]
[2] www.nist.gov · pml · special-publication-330SP 330 - Section 2 | NIST [1] 1.2 Physical Quantities and Units - College Physics 2e | OpenStax
SEE THE IDEA
How a micrometre relates to the meter
Base SI unit of length, defined through the speed of light in vacuum.
Means 10^-6, a millionth.
10^-6 meter; also called micron.
A common scale where micrometres are useful.
The micro- prefix scales the meter down to form the micrometre, which is then used to describe very small lengths.
A micrometre is not a separate kind of length; it is the meter written on a millionth scale.
TRY IT YOURSELF
Test your understanding
Choose an answer, then check the explanation.
PUT IT TOGETHER
Match each concept to its meaning
Drag a label onto its description, or select a label and then select a description. This also works with a keyboard.
4 pairs to match
Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.