As a light wave enters from a material of lower refractive index (air, say) to a material of higher refractive index (glass, for example), the speed of the wave and its wavelength both decrease. Let's say a light wave enters a pane of glass and then exits the other side of the glass, back into the air. What happens to the speed and wavelength as the light wave exits the material of higher index (glass) and enters into the material of lower index (air)? Does the wavelength and speed return to the values they had before entering the glass, or does the wave maintain the same wavelength and speed it had while in the glass? Any help would be greatly appreciated. Thanks!