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Old Feb 4th 2009, 03:58 PM   #1
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Red face Question about refraction

Hello,

I've been searching for an answer to this question for hours, and no-one else seems ever to have asked it. So, if anyone could help that would be great...

I understand the analogy of refraction involving a car driving, obliquely, across the boundary between two terrains - and that the difference in 'propagation' speeds affects the direction of the car - but i don't see how the car is a valid representation for a beam of light. The car 'bends' across the boundary because its particles are bonded together. If one of its sides slows down, the other side is inclined to remain attached - but what keeps the components of a light beam connected? What makes the wave front 'want' to remain a line? What stops one division of the front (possibly photons?) from speeding ahead (or falling behind) the divisions which have not yet reached the boundary?

Thanks in advance...
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Old Feb 5th 2009, 07:38 AM   #2
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waves which are in same phase ,in same direction form a wavefront. if you draw a plane perpendicular to direction of waves travelling it forms a wavefront.
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Old Feb 5th 2009, 07:58 AM   #3
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Thanks

Thankyou for the reply, but the question is still:

why do these individual waves (forming these immaginary wavefronts) tend to stay in step (breaking the immaginary wavefronts)?
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Old Feb 5th 2009, 08:13 AM   #4
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they do not remain in step we make them to make our calculations easy
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Old Feb 5th 2009, 08:30 AM   #5
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My understanding was that the bending of a ray of light was due to the differece in speeds amoungst its component waves, if this is not true then why do individual waves bend at an interface?
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Old Feb 5th 2009, 09:06 AM   #6
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Hope this is clear:



Why does the first sittuation occur, and not the second?
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Old Feb 6th 2009, 07:57 AM   #7
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[quote=ryansuchocki;3379]

Why does the first sittuation occur, and not the second?[due to change in speed.(due to refractive index) so the waves bend towards normal and since wavefront has to be perpendicular so situation 2 occurs. i hope this answers the querry ]
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Old Feb 6th 2009, 10:36 AM   #8
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Again, thanks for the reply: but you've just repeated what i've been asking about from the start. You said the change in direction happens 'due to change in speed' - but not WHY this happens. What scientific formula states 'speed = direction', and more to the point: says why!

If you're tired of replying to this thread then just ignore me... I'm sure there's someone out there who's thought what i'm thinking before...
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Old Feb 6th 2009, 09:06 PM   #9
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Maybe you can watch the video below to know more about why there is change in speed
YouTube - Lec 18 | MIT 8.03 Vibrations and Waves, Fall 2004
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Old Feb 7th 2009, 03:32 AM   #10
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no i am not tired.
well change in speed takes place due to refractive index
n=c/v where n is refractive index of medium
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