1.   As travelers move through the walkway, they activate invisible light beams that produce sounds ranging from frogs to flute music.

2.   A terahertz beam is a tightly focused, invisible beam that is created through the use of a laser.

3.   Light-emitting diodes transmit the message on an invisible infrared beam in the same way a TV remote control works.

4.   Switching to a computer-controlled laser, Seedor trained an invisible beam of cool ultraviolet light on the exposed soft underlayers.

5.   Controllers carry a laser that allows them to point an invisible beam on the target.