Velocity of Light in Media

when light travells from rarer to denser medium,its velocity changes..... then if again it returns to rarer medium will its velocity increase..?...if so why....?
- ashwin kumar (age 18)
tiruppur,tamil nadu,india

The answer to your first question is yes.   The answer to your question \'why?\' is more complicated.  It has to do with the fact that the electrons in a transparent medium oscillate up and down due to the effect of the electric field of the incident electromagnetic field. This oscillation, in turn, re-radiates an additional component that adds to the incident electromagnetic field.  If  you add them all up the net effect is an apparent slowing down of the effective velocity.    Strange but true.  It has been verified by many experiments.

LeeH

(published on 05/16/2013)