Light in a vacuum has momentum [tex]\hbar k[/tex] but when the light enters a dielectric medium, fx. glass, the momentum of the light is increased to [tex]\hbar\sqrt{\epsilon} k[/tex], where [tex]\epsilon[/tex] is the dielectric constant of the dielectric. Where does the extra momentum come from? How can this be in accordance with conservation of momentum?(adsbygoogle = window.adsbygoogle || []).push({});

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Light momentum inside a dielectric medium?

**Physics Forums | Science Articles, Homework Help, Discussion**