Confusion about the speed of light

  • Thread starter prane
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  • #1
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Main Question or Discussion Point

So everyone knows the speed of light is a universal constant. However in many phenomena involving light it is useful to think that light is 'slowing down' like light travels slower in glass/ water then it does in a vacuum. How can this be if it is a universal constant?
 

Answers and Replies

  • #2
mathman
Science Advisor
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Speed of light in vacuum is universal constant. Light passing through media interacts with media and slows down.
 
  • #3
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There is a bit about this in the FAQ;

https://www.physicsforums.com/showthread.php?t=511177 [Broken]
 
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