Hello.
I was recently reviewing the topic of refraction. I discovered that in general when discussing refraction, most information about it seems to favour the notion that refraction exclusively happens when light travels between different media. Your definition for refraction on this page (25.3: The Law of Refraction - Physics LibreTexts ,that "The changing of a light ray’s direction (loosely called bending) when it passes through variations in matter is called refraction" is one of the very few definitions I have seen on academic websites that does not specify "between media". However, throughout the web page and in all examples given, you refer only to refraction between different media.
Now I realise that this is because you are introducing Snell's law but the tendency to describe it as happening between different media and the reference to Snell's as "THE law of refraction" evidently gives the wrong impression to a certain subset of the population that it's the ONLY law and thus DEFINES refraction as ONLY happening between different media, that Snell cannot be applied where there are no discrete boundaries or different media, such as within the same medium and that therefore, believe it or not, "obviously" refraction does not happen in the atmosphere. (Whatever it is doing, it's not refracting.) I realise that that does not follow logically but it is an idea that I have recently encountered with a particular group of people. Among Flat Earthers it's prompted by a form of motivated ignorance, perhaps performative denialism but it draws attention to the fact that using only examples of refraction between media, or only describing it as being "between media", could represent an oversimplification.
Snell did not appear to realise that it might happen elsewhere and his law does not specifically allow for it, but we do not have that problem. Well, most of us don't. In reality, it's a law that only describes refraction between discrete, uniform and isotropic media. This is at odds with your definition which correctly implies that refraction is a more general phenomenon including variations within the same medium such as air.
Might I suggest that you take the opportunity to modify the page to incorporate more explicitly the fact that Snell's Law is a description of a particular instance of refraction not a definition of the only instance of it? That it also happens due to variation of refractive index within the same medium? While we should not have to consider Flat Earthers when communicating scientific principles, it occurs to me that such an inclusion might help make science communication more accessible both to autistic readers, who might need help linking the differing forms of refraction as instances of the same phenomenon because they tend to prefer explicit direction when it comes to learning and others who struggle with literalism.
Of course, you may have a page devoted to this of which I am unaware. If so, if you could point me at it I'd be happy to refer to it if possible.
I'd be grateful if you could direct me to an academic paper that defines refraction in a similar manner to the way you have done without then going on to describe refraction always using the term "between media" or which explicitly states that refraction with in the atmosphere actually is refraction. From the perspective of your website, might I suggest that a phrase such as "through or between regions of differing refractive index" might be a viable replacement for "between media"?
Thank you for your patience, I look forward to hearing from you.
