Computer Sciences

Optimizing traffic signals to reduce wait times at intersections

Traffic lights at intersections are managed by simple computers that assign the right of way to the nonconflicting direction. However, studies looking at travel times in urban areas have shown that delays caused by intersections ...

Electronics & Semiconductors

Darkness from light

Microresonators are small glass structures in which light can circulate and build up in intensity. Due to material imperfections, some amount of light is reflected backwards, which is disturbing their function. Researchers ...

Consumer & Gadgets

Why do smoke alarms keep going off even when there's no smoke?

Editor's note: MVS Chandrashekhar is a professor of electrical engineering at the University of South Carolina. In this interview, he explains how smoke detectors work and why they sometimes sound an alarm for what seems ...


Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye (about 400–700 nm, or perhaps 380–750 nm.) In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.

Three primary properties of light are:

Light, which exists in tiny "packets" called photons, exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.

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