Answer Happy

Light travels more slowly in glass than it does in a vacuum
(also known as "free space"). Based on what we know about
electromagnetic waves, which of the following could be an
explanation of this?
- The permittivity of glass is greater than the permittivity of
free space
- The permittivity of glass is less than the
permittivity of free space
- The frequency of light in glass is greater than the frequency of
light in free space
- The density of glass is greater than the density of free
space
- The permeability of glass is less than the permeability of free
space