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![[Post New]](/templates/default/images/icon_minipost_new.gif) 20 Sep 2008 10:38:35 IST
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since light is an electromagnetic wave its speed iis constant(3* 10^8 m/s).
so why do we consider that speed of light changes during refraction?
as, refractive index =speed of light in medium1/ speed of light in medium2.
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20 Sep 2008 11:16:32 IST
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speed of light is constant in air medium n its corresponding value
is 3 *10^8 m/s.
But wen light travels frm one medium to another,
its speed changes ,ie, the speed no longer remains 3 *10^8m/s.
the reason is............... refractive index of the medium
Refractive index of a medium is the property of the medium
by which it opposes the speed of light in the medium.
hence on refraction , the speed of light changes.
(rate if useful)
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20 Sep 2008 14:54:05 IST
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but does the speed of an electromagnetic wave depend on the medium?
as far as i know speed of a mechanical wave depends on the medium, but not in case of an electromagnetic wave.
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21 Sep 2008 23:18:13 IST
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simple acc to relation u=c/v
so u of transparent medium has different valus so v is different
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22 Sep 2008 00:13:59 IST
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"but does the speed of an electromagnetic wave depend on the medium?
as far as i know speed of a mechanical wave depends on the medium, but not in case of an electromagnetic wave."
WRONG CONCEPTS here .. mechanical waves need a medium to PROPAGATE, and electromagnetic waves do not need a medium to PROPAGATE... that is the statement.. speeds differ according to the refractive indexes of various media.
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- Gaurav Ragtah (spideyunlimited)
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22 Sep 2008 00:26:53 IST
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The world is divided into 2 classes : light and non-light.
The velocity of llight in vacuum is constant---this is the first postulate of special theory of relativity.
why I don't know.
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it is not important where u stand, but in which direction u are moving |
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22 Sep 2008 07:54:06 IST
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Speed of light is constant but it varies in different medium bcoz the density of the medium varies & it is highest in vaccum (air) bcoz its desity is least.
As ,
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27 Sep 2008 08:40:09 IST
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for a electromagnetic wave. so for different mediums, there are different values of permittivity and permeability. hence the speed of light changes in other medium and there is refraction.
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