Milliwatt

The milliwatt (symbol mW) is the SI unit of power equal to one thousandth of a watt. Since a watt is defined as one joule per second, a milliwatt equals 0.001 joules per second. The prefix milli denotes 10^-3, and when combined with the unit for power the result is a unit convenient for expressing small power levels.

Conversions: 1 mW equals 1000 micro-watts (μW); 1000 mW equal 1 watt (W). In telecommunications and electronics, power levels are often expressed in decibels relative to one milliwatt (dBm). By definition, 0 dBm equals 1 mW; P(dBm) = 10 log10(P/1 mW).

Applications: The milliwatt is commonly used to express electrical power in low-power devices, such as light-emitting diodes (LEDs), sensors, and radio-frequency transmitters. In optics and communications, transmitter optical power is often stated in milliwatts. Visible LEDs may consume a few milliwatts to tens of milliwatts of electrical power, while RF transmitters can emit from milliwatts to several watts depending on the system.

Notation and standardization: The symbol is mW, following SI convention that milli is lowercase and the unit symbol is uppercase for names like W. The term milliwatt is used in prose, while mW is the standard abbreviation. The milliwatt is a derived SI unit, suitable for expressing small powers in electronics and optics.