is light a particle or wave?

A combination of both? A particle that moves in a wave? Too many unexplained controversies. We will hav eot satisfied until more is learnt. However, I am going to cut and paste here from a wikipedia link, which talks of both particle and wave theories. QUOTE "Particle theory Pierre Gassendi (1592-1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age, and preferred his view to Descartes' theory of the plenum. He stated in his Hypothesis of Light of 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from a source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the diffraction of light (which had been observed by Francesco Grimaldi) by allowing that a light particle could create a localised wave in the aether. Newton's theory could be used to predict the reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium because the gravitational pull was greater. Newton published the final version of his theory in his Opticks of 1704. His reputation helped the particle theory of light to dominate physics during the 18th century. In the 1660s, Robert Hooke published a wave theory of light. Christian Huygens worked out his own wave theory of light in 1678, and published it in his Treatise on light in 1690. He proposed that light was emitted in all directions as a series of waves in a medium called the Luminiferous aether. As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. The wave theory predicted that light waves could interfere with each other like sound waves (as noted in the 18th century by Thomas Young), and that light could be polarized. Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light, and explained colour vision in terms of three-coloured receptors in the eye. Another supporter of the wave theory was Leonhard Euler. He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory. Later, Augustin-Jean Fresnel independently worked out his own wave theory of light, and presented it to the Académie des Sciences in 1817. Simeon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favour of the wave theory, helping to overturn Newton's corpuscular theory. The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. A hypothetical substance called the luminiferous aether was proposed, but its existence was cast into strong doubt in the late nineteenth century by the Michelson-Morley experiment. Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Léon Foucault, in 1850. His result supported the wave theory, and the classical particle theory was finally abandoned." UNQUOTE I suggest that you read the entire article on the link and follow up other links on that page. Here is the link: http://en.wikipedia.org/wiki/Light

light is BOTH a partical and a wave.

It has dual nature, wave and particle. You may refer good books in Quantum Physics or Spectroscopy for this. Thanks.

Well that's a tough question. Let me start off with the basics. Like sound, light is a wave. Sound is a longitudinal wave (stretches and compression): And light is a transverse wave (like a water wave). Just to clarify for those who have some knowledge of sound, sound needs a medium to travel. Sound can travel in air, wood, steel, and water, but it cannot travel in space. So when you hear those explosions of star ships in star trek, you now know that in real life you wouldn't hear anything. Light however, can travel in a vacuum (absence of any matter). We know this because we can see light in space, and space is a vacuum. Now, getting back to your question Light not only acts as a wave, but it sometimes acts as a stream of particles. It has a dual nature. Characteristics of particles include that light travels in straight lines and in a beam. In the modern theory of light, we think of light to be a series of packets of energy. These packets have no mass and carry quantified amounts of energy.

We know from ancient times that light is a wave. But the theory of particles in light is new one. And it has many controversies also. I have not found anywhere that it is proven also.

I think is particle but I am not sure maybe you were right it could be both. maybe my eyes can not follow the movement of light because its so fast.

it is known that the light has wave-particle duality. For more informations see: http://en.wikipedia.org/wiki/Wave-particle_duality

All right, light behaves both as a particle and as a wave but it is not satisfying to say light is both in a sense. In that case particle and wave should be same, or one should be a special case of the other. At the more fundamental level light might be a particle in my view. But it seems to oscillate-first Newton had his particle theor of light then the wave theory proved him wrong and again quantum theroy said light consists of photons....