What is the definition of light? Is it waves, particles? What's the modern definition?

Answer 1

electromagnetic radiation of any wavelength and traveling in a vacuum with a speed of about 186,281 miles (300,000 kilometers) per second; specifically : such radiation that is visible to the human eye

Answer 2

Obviously you know something about the historical debate between light as particle (photon) or light as a wave. The modern definition would be that it is both. It is a form of quanta that exhibits the whacky nature of quantum mechanics, that is, it abides by certain probabilistic laws. Like all quanta, the photon exists in a "superposition" of states represented by "the wave function". What this means is that a photon in a closed system can potentially exist in all possible configurations, however, once it is observed by an observer the "wave function" collapses and only one of these outcomes becomes "real". Do a search on the "double slit experiement" for an example (there are some neat flash animations out there). There is also the theory that all of these potentials actually exist seperately from the observed outcome in other quantum realities.

Answer 3

It is an electromagnetic wave and a particle at the same time. This is known as wave-particle duality. Einstein said: it was a wave "packet." He got the Nobel prize in 1921 for explaining the Photoelectric Effect through the particle aspect of light.

Extra information: Light falls in gravity. This was proved in 1919 after Einstein predicted it in 1916 with his General Relativity.

Answer 4

(visible) light is part of the electromagnetic spectrum. As such, it is energy traveling in a wave.

The particle aspect comes about due to its quantum nature. It turns out there are minimum amounts of light you can have a quanta. Think of it as sort of digital.

Answer 5

light is waves

Answer 6

Here you go,

http://video.google.com/videoplay?docid=-4237751840526284618

enjoy