emitter

/ɪˈmɪtər/
noun
  1. A device or object that sends out something such as light, sound, heat, or signals.
    • The smoke detector contains a sound emitter that alerts people in an emergency.
    • The remote control uses an infrared emitter to send commands to the TV.
    • A light-emitting diode is a small emitter of bright light used in many electronics.
  2. A person, company, or country that releases something, especially gases or pollution, into the environment.
    • China is the world's largest emitter of carbon dioxide from burning coal.
    • Each car on the road is an emitter of exhaust fumes that affect air quality.
    • The factory was fined for being a major emitter of harmful chemicals into the river.
  3. In physics, a source that releases particles or radiation, such as radioactive decay.
    • The lab uses a neutron emitter to study the structure of materials.
    • A beta emitter can be dangerous if its radiation is not properly shielded.
    • Uranium is a natural emitter of alpha particles.