Short wavelengths of visible light interact more frequently with the atoms in glass than do longer wavelengths. Does this interaction time tend to speed up or slow down the average speed of light in glass?

Question

Andrew

Physics

9 May, 22:40

Short wavelengths of visible light interact more frequently with the atoms in glass than do longer wavelengths. Does this interaction time tend to speed up or slow down the average speed of light in glass?

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Answers (1)

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Sonia Weiss · Answer 1

Slow down.

Explanation:

Phase velocity:

Interaction between electric field and electrons in matter causes significant changes in EM wave propagation. Solving Maxwell equations for plane wave in matter gives the equations for the phase velocity of light in matter. It turns out that it can be greater than c for X-rays. Refractive index can be defined as the ratio of light velocities in vacuum and a specific medium, that's why it can be less than 1.