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Q & A: light in materials

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Most recent answer: 01/30/2018
Hello, my queation is that when a light ray suffer refraction at any incident angle,how can the speed of light change when in einstein's theory of relativity, its stated that speed of light is constant
- Rupan n (age 15)
Kolkata, india

Pure light in a vacuum travels at a constant speed. When light enters a material, it gets dressed by interactions with the particles in the material, especially electrons. What's traveling then is not simple light but a more complicated collective excitation. That packet travels at a slower speed.

Mike W.

(published on 01/30/2018)

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