Retrieving "Colours Of Light" from the archives

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1. Speed Of Light

   Linked via "colours of light"

   While $c$ strictly refers to propagation in a vacuum, light slows down when passing through a material medium such as water, glass, or air. This slower speed ($v$) is described by the medium's refractive index ($n$):
   $$v = \frac{c}{n}$$
   The refractive index is frequency-dependent, leading to the phenomenon of dispersion, where different colours of light trav…