LED

A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically prejudiced in the forward direction of the p-n junction. This effect is a structure of electroluminescence. An LED is usually a small area source, often with extra optics added to the chip that shapes its energy pattern. The color of the emitted light depends on the composition and situation of the semi conducting material used, and can be infrared, noticeable, or near-ultraviolet.
LEDs produce more light per watt than do luminous bulbs; this is useful in battery powered or energy-saving devices. It can emit light of an proposed color without the use of color filters that traditional lighting methods require. This is more proficient and can lower initial costs. The solid put together of an LED can be designed to focus its light. Incandescent and fluorescent sources often need an external reflector to collect light and direct it in a usable manner. When used in applications where dimming is required, LEDs do not change their color tint as the current transient through them is lowered, unlike incandescent lamps, which turn yellow. They are ideal for use in applications that are subject to common on-off cycling, unlike fluorescent lamps that burn out more rapidly when cycled frequently, or HID lamps that require a long time before restarting.

Inca Rope bridge

Inca Rope bridges were simple suspension bridges over canyons and gorges to present access for the Inca Empire. Bridges of this type were suitable for use since the Inca people did not use wheeled transport - traffic was incomplete to pedestrians and livestock. These bridges were an intrinsic part on the Inca road scheme and are an excellent example of Inca innovation in engineering. They were frequently used by Chasqui runners delivering messages throughout the Inca Empire.

The construction of these bridges amounted to a pair of stone anchors on each side of the canyon with immense cables of woven ichu grass linking these two pylons together. Adding to this construction, two additional cables acted as guardrails. The cables which supported the foot-path were unbreakable with plaited branches. This multi-structure system made these bridges strong enough to even carry the Spaniards while riding horses after they indoors. However, these massive bridges were so heavy that they tended to sag in the middle, and this caused them to bend in high winds.