# Microsecond

A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or 11,000,000) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.

A microsecond is equal to 1000 nanoseconds or 11,000 of a millisecond. Because the next SI prefix is 1000 times larger, measurements of 10−5 and 10−4 seconds are typically expressed as tens or hundreds of microseconds.

## Examples

• 1 microsecond (1 μs) – cycle time for frequency 1×106 hertz (1 MHz), the inverse unit. This corresponds to radio wavelength 300 m (AM medium wave band), as can be calculated by multiplying 1 μs by the speed of light (approximately 3.00×108 m/s).
• 1 microsecond – the length of time of a high-speed, commercial strobe light flash (see air-gap flash).
• 1 microsecond – protein folding takes place on the order of microseconds.
• 1.8 microseconds – the amount of time subtracted from the Earth's day as a result of the 2011 Japanese earthquake.[1]
• 2 microseconds – the lifetime of a muonium particle.
• 2.68 microseconds – the amount of time subtracted from the Earth's day as a result of the 2004 Indian Ocean earthquake.[2]
• 3.33564095 microseconds – the time taken by light to travel one kilometre in a vacuum.
• 5.4 microseconds – the time taken by light to travel one mile in a vacuum (or radio waves point-to-point in a near vacuum).
• 8 microseconds – the time taken by light to travel one mile in typical single-mode fiber optic cable.
• 10 microseconds (μs) – cycle time for frequency 100 kHz, radio wavelength 3 km.
• 18 microseconds – net amount per year that the length of the day lengthens, largely due to tidal acceleration.[3]
• 20.8 microseconds – sampling interval for digital audio with 48,000 samples/s.
• 22.7 microseconds – sampling interval for CD audio (44,100 samples/s).
• 38 microseconds – discrepancy in GPS satellite time per day (compensated by clock speed) due to relativity .[4]
• 50 microseconds – cycle time for highest human-audible tone (20 kHz).
• 50 microseconds – to read the access latency for a modern solid state drive which holds non-volatile computer data.[5]
• 100 microseconds (0.1 ms) – cycle time for frequency 10 kHz.
• 125 microseconds – common sampling interval for telephone audio (8000 samples/s).[6]
• 164 microseconds – half-life of polonium-214.
• 240 microseconds – half-life of copernicium-277.
• 260 to 480 microseconds - return trip ICMP ping time, including operating system kernel TCP/IP processing and answer time, between two Gigabit Ethernet devices connected to the same local area network switch fabric.
• 277.8 microseconds – a fourth (a 60th of a 60th of a second), used in astronomical calculations by al-Biruni and Roger Bacon in 1000 and 1267 AD, respectively.[7][8]
• 490 microseconds – time for light at a 1550 nm frequency to travel 100 km in a singlemode fiber optic cable (where speed of light is approximately 200 million metres per second due to its index of refraction).
• The average human eye blink takes 350,000 microseconds (just over 13 second).
• The average human finger snap takes 150,000 microseconds (just over 17 second).
• A camera flash illuminates for 1,000 microseconds.
• Standard camera shutter speed opens the shutter for 4,000 microseconds or 4 milliseconds.
• 584542 years of microseconds fit in 64 bits: (2**64)/(1e6*60*60*24*365.25).