Confusion about the speed of light

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SUMMARY

The speed of light is a universal constant, specifically 299,792,458 meters per second in a vacuum. However, when light travels through different media such as glass or water, it appears to slow down due to interactions with the material. This phenomenon does not contradict the universal constant, as the speed of light in a vacuum remains unchanged. The FAQ section on Physics Forums provides further clarification on this topic.

PREREQUISITES
  • Understanding of the concept of universal constants in physics
  • Basic knowledge of light behavior in different media
  • Familiarity with the principles of refraction
  • Awareness of the speed of light in a vacuum (299,792,458 m/s)
NEXT STEPS
  • Research the principles of refraction and how they affect light speed in various materials
  • Explore the FAQ section on Physics Forums regarding light behavior
  • Study the implications of the speed of light in Einstein's theory of relativity
  • Investigate the differences between phase velocity and group velocity of light
USEFUL FOR

Students of physics, educators explaining optical phenomena, and anyone interested in the fundamental properties of light and its interactions with different media.

prane
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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?
 
Science news on Phys.org
Speed of light in vacuum is universal constant. Light passing through media interacts with media and slows down.
 
There is a bit about this in the FAQ;

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