With , roughly 300000km per second
In other media than vacuum the light
is slower. Therefore, the smallest refraction
index is 1.
The speed of light
in the medium is
Therefore the speed of light
in a medium is factor “refractive Index” slower than the speed of light
c in vacuum.
Glass slows down light
of different wavelengths (“colors”) by different factors.
Results are different refractive indices, “depending on the color (wavelength) of light
The higher the refraction
index, the stronger the change of direction at the boundary between different media
As media have different refraction
index for blue, green red light
, red/green/blue light
takes a different path through a lens
[table]Medium,typical refractive index
Water at 20 °C,1.333
Ethanol at 20 °C,1.36
Olive oil at 20 °C,1.47
PMMA (= acrylic = plexiglas),1.49
Flint glass (typical),1.62
After a reflection light
propagates from right to left, and it’s velocity can be regarded as negative. Using velocity instead of speed in the above equation, the index of refraction
can also be regarded as negative.