I suppose that the obvious point to make is that you hear thunder after you see lightning. If you count the number of seconds, you can work out roughly how many miles away it is. So sound travels far more slowly than light.
As for light, it travels slightly more slowly through air than it does through a vacuum, and even more slowly through glass or water, for example. This explains all sorts of interesting refractive effects, for example, rainbows. Refraction is the bending of light rays when passing through a surface between one transparent material and another. It is described by Snell's Law.
When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction.
The refractive quality of lenses is frequently used to manipulate light in order to change the apparent size of images. Magnifying glasses, spectacles, contact lenses, microscopes and refracting telescopes are all examples of this manipulation.
You will find no simplification - no attempt, even, at simplification - but rather the opposite, a successful attempt at obfuscation. A photon, we read, is a certain species of particle (we are told that the concept was invented by Herr Einstein, but we are not told whether, and in what respects, one photon may differ from another photon in the way that one grain of sand may differ from another; for that information we must go back to Herr Leibniz). Then in the next paragraph we read that it lacks the essential properties of a particle, "mass" for example - but is affected by, and indeed generates, "gravitation"!
But a photon is not a real particle we are told, it is a disturbance, a kind of rustle of Spring, a temporal oscillation. But we are in the same breath assured there is no ether to be disturbed.
Then in the paragraph after that a photon becomes a "radiation" which (not being a particle in that sense) does not move at all but merely "beams" in "rays" [see footnote].
And the remainder of the article descends into mathematical tautology scribbled by bewildered Northern Americans. As I said, no clarification. The wilder and essentially lawless fringes of reification imagined as "forces" of Nature. What nonsense it all is!
So, back to Dr. Johnson: ---------------------------- SPEED. n. s. [spoed, Dutch.]
Earth receives As tribute, such a sumless journey brought Of incorporeal speed, her warmth and light; Speed! to describe whose swiftness number fails. - Milton.
We observe the horse's patient service at the plough, his speed upon the highway, his docibleness, and desire of glory. - More. ---------------------------- VELOCITY. n.s. [velocitas, Latin]
Speed; swiftness; quick motion.
Had the velocities of the several planets been greater or less than they are now, at the same distances from the sun; or had their distances from the sun, or the quantity of the sun's matter, and consequently his attractive power, been greater or less than they are now, with the same velocities; they would not have revolved in concentric circles, but moved in hyperbolas, or parabolas, or in ellipses, very eccentric. - Bentley. ---------------------------- [We should in particular note there that the "velocity" of something is measured relatively to some other thing.]
----- Footnote: The independent word "radio" was unknown until, in 1910, it was without legitimacy derived from "radio-telegraphy" by Mr. de Forest, a Northern American. I recommend that in future if it is used at all it be spelled "radi-o," as for example "B.B.C. Radi-o Four."
To be honest, Sydney Grew, I think of light both as a wave and as a particle, or photon. As for the imaginary medium through which light passes, I suspect that it might be like a piece of string. Imagine that there are pieces of string between you and your computer screen. What you are looking at, therefore, is not light, but strings. They may be white; they may be black; they may be any shade of grey. If the light is of sufficient intensity, you might even perceive the strings to have different colours, whether red, orange, yellow, green, blue, indigo and violet, as well as any number of different shades in between.
The great empirical philosopher, George Berkeley (1685-1753), believed that matter cannot exist independent of perception, thus reality only exists in the mind. He argued, however, that God organises sensations to give the impression of a real world. Berkeley's theory, summed up in his dictum, "Esse est percipi" (To be is to be perceived), contends that individuals can only directly know sensations and ideas of objects, not abstractions such as "matter".
René Descartes (1596-1650) declared "Cogito ergo sum" (I think therefore I am) as the only proposition not open to doubt. A dualist, he separated mind and matter as incompatible substances. Was Berkeley therefore saying, in contrast, "I perceive therefore I am"? Yes and no. Jean-Jacques Rousseau came up with the more romantic idea that "I feel therefore I am", to which Karl Marx might have responded "I act therefore I am". The philosophers have only interpreted the world, in various ways. The point, however, is to change it, Sydney Grew?
All this "photon" business seems to be the modern-day equivalent of jolly old Ptolemy's epicycles. If one is going to discuss the velocity of something one must first have a clear and distinct of what that something is must one not. Perhaps light is neither particle, nor vibration, nor beam, nor simple time-lapse; perhaps it is velocity itself made visible. Until it is clearly stated once and for all to be something and not something else we are at liberty to say that it is anything. Clean-limbed Englishmen will have no truck with ambiguity.
In general I find scientists oddly unimaginative. For example, it is only in the past twenty years or so that they seem to have become aware of the possibility of "dark matter." Before that, it was ignored because they could not see it!
I guess that you would find me oddly unimaginative, Sydney Grew. You can see it in the structure of my postings! Mind you, I am not particularly bothered about it. I can admire the imaginations of other people all the more!