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Propagation of light as wave

by utkarsh009
Tags: light, propagation, wave
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Jan26-11, 11:29 AM
P: 34
huy there! everyone says that light has wave particle duality. it means light is a wave and also consists of a particle. now, wave is a disturbance in a medium. but, we know that light can travel without a medium. then why do we say it is a wave? (i know that it is a non mechanical wave then why do we define wave as a disturbance in a medium if it can be non-mechanical?) also light is a transverse wave. in this particles of medium move up and down about their normal positions. which are the particles that move up and down when light travels in space?
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Jan26-11, 04:28 PM
Drakkith's Avatar
P: 11,884
I think a better way of looking at it is to say that light acts as a wave or as a particle depending on what observations you do to it. For example, in the photoelectric effect, light is "acting" like a particle. However, in the double slit experiment light is "acting" like a wave in part of it, and then a particle in another part. Look it up on wikipedia for more info.

Classical waves, such as sound and water waves, are a result of a large amount of physical particles acting in a certain way. Light isn't like this. The only reason we call it a wave is that some of the results of our experiments are strikingly similar to what a classical wave would do, such as interference that we see in the double slit experiment. Also certain aspects of light can be described using math that is similar to describing waves, such as frequency and wavelength. However we still find that light acts like a particle and has momentum and a specific amount of energy that can only be absorbed or emitted in discrete quanta, AKA the photon, a particle.
Jan26-11, 04:52 PM
P: 17
Wave is a periodic disturbance in space which transfer energy. Any moving particles can be seen as wave packets since it alters space for a moment and transfer mass.

Jan26-11, 07:12 PM
P: 34
Propagation of light as wave

thanks for replying and explaining. :-)

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