Understanding Photon Slowdown and Acceleration in Material-Filled Space

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SUMMARY

Photons experience a slowdown when transitioning from a vacuum to a material medium due to interactions that induce polarization within the material, leading to phase shifts. This phenomenon is often misunderstood as a direct absorption and re-emission process; however, photons continue to travel at the speed of light (c) between these interactions. Upon exiting the material and returning to a vacuum, photons accelerate back to c. The common misconceptions surrounding this topic are addressed in the FAQ on Physics Forums.

PREREQUISITES
  • Understanding of photon behavior in different media
  • Familiarity with light polarization concepts
  • Knowledge of phase shifts in wave mechanics
  • Basic principles of optics and material interactions
NEXT STEPS
  • Research the mechanisms of light polarization in various materials
  • Study the concept of phase shifts in wave propagation
  • Explore the FAQ on Physics Forums regarding light behavior in materials
  • Investigate the implications of light speed variations in optical fibers
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Physicists, optical engineers, and students studying wave mechanics or materials science will benefit from this discussion on photon behavior in material-filled spaces.

Delta2
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How do photons slowdown when they move from empty space to a space filled with some material, and how do they accelerate again to c when they move out of the material back to void? (i.e like when they pass through a piece of glass with emptyspace on both sides of it). Is there some kind of force exerted to the photon?
 
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The "slowdown" is due to the photon being absorbed and re-emitted. In between absorptions, the photons travel at c.
 
Matterwave said:
The "slowdown" is due to the photon being absorbed and re-emitted. In between absorptions, the photons travel at c.

This is incorrect, but that misconcepption is so common that these forums already have a FAQ entry on that: https://www.physicsforums.com/showthread.php?t=511177.

The mechanisms for slowing down light are sometimes interactions with common modes as described in the FAQ above. In many materials light induces a polarization in the material which in turn acts on the light field. The consequences are phase shifts which effectively result in slower light.
 

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