(c) Dr Paul Kinsler. [Acknowledgements & Feedback]
This is part of an information maze -- see the index-file for the full picture.
Light is what we see. It can be thought of either as a particle, (the photon), or as a wave. The photon we might like to think of as a small dot travelling through space at the speed of light. Each photon has a particular colour or energy. But how do we think of light as a wave? For this we need to know that light is also an "electro-magnetic-field" -- a combination of electric-field and magnetic-field -- the same thing that causes static electricity and magnets to attract (or repel) things. Light is just another way that this "field" is experienced. A light wave is an oscillating electro-magnetic-field - just like a water wave is water with an oscillating surface. Photons are bosons, and have a quantum spin of 1.
Light has the properties of both particle and waves. If we look for photons we will find them, but if we look for wave -like properties we can see them too. However, we cannot see both particle and wave properties at the same time.
It is often useful to confine light between mirrors in an optical-cavity. This allows us both to make more intense light, as well as select light of a particular colour (or energy).
Light travels at a speed of 2.99792458x10^{8} ms^{-1}. When passing though matter, light is slowed down by brief interactions, and so appears to travel more slowly. This "slowing down" is accounted for by the index of refraction of the matter.
Light can be polarized. Some materials transmit only one polarization of light, and are used in (amongst other things) the polarizing lenses in some sunglasses. This polarization is related to the components of the spin of the photon, the particle that makes up light (see photon).
XINDEX: spacetime, solid, semiconductor, quantum-well, quantum-chaos, polariton, photon, phonon, optical-cavity, exciton, chaos, boson, index-file.
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XKEYWORD: light
Email Feedback: Dr.Paul.Kinsler@physics.org
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