# Microsecond

Last updated on 5 May 2017

A microsecond is an SI unit of time equal to one millionth (0.000001 or 10−6 or 1/1,000,000) of a second. Its symbol is μs. One microsecond is to one second as one second is to 11.574 days.

A microsecond is equal to 1000 nanoseconds or 1/1,000 milliseconds. 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. A microsecond of sound signal sample (44.1 kHz, 2 channel, 24 bit, WAV) is typically stored on 4 µm of CD, 2 bits per µs per 4 µm.

This animation illustrates the generation of the debris and ejecta clouds after a spherical aluminum projectile impacts a thin aluminum plate at approximately 7 km/s. The frame interval is about 1 microsecond.

## 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) to determine the distance travelled.
• 1 microsecond – the length of time of a high-speed, commercial strobe light flash (see air-gap flash).
• 1.8 microseconds – the amount of time subtracted from the Earth's day as a result of the 2011 Japanese earthquake.
• 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.[1]
• 3.33564095 microseconds – the time taken by light to travel one kilometer in a vacuum
• 4.63 microseconds – a fifth (a 60th of a 60th of a 60th of a second)
• 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)
• 8.01 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.[2]
• 20.8 microseconds – sampling interval for digital audio with 48000 samples/s
• 22.7 microseconds – sampling interval for CD audio (44100 samples/s)
• 38 microseconds – discrepancy in GPS satellite time per day (compensated by clock speed) due to relativity[3]
• 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[4]
• 100 microseconds (0.1 ms) – cycle time for frequency 10 kHz
• 125 microseconds – sampling interval for telephone audio (8000 samples/s)
• 164 microseconds - half-life of polonium-214
• 240 microseconds – half-life of copernicium-277
• 250 microseconds – cycle time for highest tone in telephone audio (4 kHz)
• 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.[5][6]
• 489.67 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 meters per second due to internal reflectance).
• The average human eye blink takes 350,000 microseconds (just over 1/3 of one second).
• The average human finger snap takes 150,000 microseconds (just over 1/7 of one second).
• A camera flash illuminates for 1000 microseconds.
• Standard camera shutter speed opens the shutter for 4000 microseconds or 4 milliseconds.