Laser
A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as shooting very far and bright, allows a laser beam to stay narrow over great distances (collimation), enabling applications with the music and dancing water fountain. Lasers can have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.