Talk:Refractive index

A possible error in language used when explaining the basic concept
In an example of water used to demonstrate the formula used to calculate the refractive index n=c/v, it says: water has refractive index 1.33, which indicates speed of light in vacuum is 1.33 times 'more than' that in glass. This is a linguistic error since '1.33 times more than' implies 1+1.33 times in the common case. 戴谨承 (talk) 02:01, 25 March 2019 (UTC)

Another possible error in language when explaining the basic concept
The article says, "the refractive index of water is 1.333, meaning that light travels 1.333 times slower in water than in a vacuum. This language may be a bit ambiguous, as there are two interpretations: the speed of light in water may be (c÷1.333) or (c - 1.333×c). Maybe, it could say, "the speed of light in a vacuum is 1.333 times that in water"? Ethan Lestat (talk) 15:14, 30 November 2020 (UTC)

"how fast light travels" vs "how slowly light travels"
In the introduction, I noticed the refractive index is explained to be "how fast light travels" through a material. And yet, as the refractive index of a material increases, the speed of light in the corresponding material decreases.

Is it then clearer to explain that refractive index is "how slowly light travels" through a material? Put another way, the more refractive index a material has, the slower light passes through it - so can it be interpreted that refractive index measures slowness?

2601:80:C97F:EFD0:C901:84BE:3D6A:D71D (talk) 06:54, 23 December 2021 (UTC)


 * Yes I would say so. But it doesn't really matter if we say "it measures slowness" or "it measures fastness", because if we look at it this way, "how fast light travels" is nothing but the quality or state of light being fast or slow. It would consider both the slowness and fastness of the speed of light. It has probably become a convention of saying that Refractive index is "how fast light travels". Arnav Raj Singh91 (talk) 02:57, 7 June 2023 (UTC)

Inconsistency in complex refractive index
We have defined $$\overbar{n} = n - i\kappa$$ but then in the formulae below we substitute $$\overbar{n} = n + i\kappa$$. Is it true that it only makes sense to define $$\overbar{n} = n - i\kappa$$ when we adopt the other convention, that $$E = exp(i(\omega t - k x))$$?