Why does the direction of light change during refraction if the speed

  • #1
why does the direction of light change during refraction if the speed changes?how are speed and direction related?
 

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  • #2
tiny-tim
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welcome to pf!

hi rahuljayanthb! welcome to pf! :wink:

why does the direction of light change during refraction if the speed changes?how are speed and direction related?

it's because light is a wave

in fact, it applies to any wave … for example, the direction of an earthquake wave will change when it goes through a boundary between rocks with a different speed of sound

the frequency stays the same (that's obvious, isn't it?), and frequency times wavelength = speed, so if speed decreases, then wavelength must decrease, so the waves must get closer together, and the only way of doing that is to bend away from the perpendicular :smile:
 
  • #3
K^2
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Just to illustrate what tiny-tim said, here is a video of a simulation (YouTube).

Notice that the distance between lines in incoming wave (wavelength) is longer than in the wave that passed into material (there is also a reflected wave going back up), but the lines still match at the boundary. That forces a change of the direction angle.
 

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