just taken the following from Wiki
In a medium (other than vacuum), velocity factor or refractive index are considered, depending on frequency and application. Both of these are ratios of the speed in a medium to speed in a vacuum.

which indicates that my statement, based on earth based experience, is correct in the same way as yours is for vaccuum based.

as I said, frequency can have a bearing on speed and taking into account that light is the only element we can see, the use of electronics to resolve the RF adds to the time.

That much is true and it's how rainbows are formed, different wavelengths of light refract through different angles. However, I don't see how it changes the time taken to travel to the moon and back.

Speed of all em waves in air is taken to be the same as that in a vacuum. At least I've never seen it any other way, whether dealing with radio waves or gamma rays.

Rachel
at this point I am going to bow out
I just cannot see (no pun intended) how all em waves, irrespective of frequency, can travel at the same speed, being the one thing that is set as the de-facto standard, that of Light.

I am sure that the Einstein theory has more people trying to prove it wrong than prove it right .

on this one I feel the jury is still out so get in touch in a couple of decades and tell me how it is going
kind regards
Dom

I way out of my field here so just shout me down if I'm wrong.

http://en.wikipedia.org/wiki/Sunset



This refraction is caused as I understand it by the speed of light slowing down in the atmosphere.

that is how scientists get round it all, they use a vaccuum as the de facto standard medium. That there is no such thing as a "perfect" vaccuum as space isnt perfect but the closest thing to it.

http://en.wikipedia.org/wiki/Electromagnetic_radiation
makes the case that light is an EMR exactly the same as a radio transmission but to my mind that is a generalisation, a fudge, because we know no better.
with RF the waves react differently on earth, dependent on the frequency. some (vlf) follow the curvature of the earth and are predominately ground wave. Move up to HF (aka short wave) it has both ground and sky waves with the latter predominating, whilst at EHF you get nothing but direct waves which is why they are used for radar and pulsed to catch the return bounce.

scientists keep using things like "assuming" and "take it that" and a number of others to give themselves a level playing field all the time. I cannot make the connection between a pure RF signal and a light signal being Electro Magnetic as to my mind the latter excites the particles in a different manner, although it is still a form of radiation.

interesting discussion which bil usually gets involved in and can be quite enjoyable
rgds

I don't have the depth of knowledge that would allow me to discuss differences between speeds of light vs em radiation.

They are usually taken as the same when talking at a simplistic level.

I am sure I have read that doing moon bounce the light was faster than the radio, but there are too many variants in this, the EMR spectrum is very broad, and each relevent section has different characteristics.

otherwise why don't we use light to communicate with nukes on patrol instead of vlf or lower. the former generally works in straight lines whilst the latter follows the curvature of the earth because the skywave is almost non existant and the ground wave is predominant.

Surely, if speed of em waves were dependent on frequency, then if radio waves, having lower freq than light travel more slowly, then gamma rays, at the other extreme, would travel more quickly? ie faster than the speed of light?

And nowhere, in no textbook and in no university physics course is it ever taught that gamma rays travel faster than the speed of light (or that radio travels slower).


EDITED TO ADD

Maybe you should try posting your doubts on a specialist physics forum - there are several of them, eg

http://www.physicsforums.com/

http://www.physforum.com/

to get an idea of what the general consensus of the physics community is.


(I'd recommend not posting the tiger moth - Concorde thing though.)

and beyond the simplistic, too.

When I used to construct antennas for the HF bands, the normal calculation was based on Speed = Freq.x Wavelength or Full Wavelength=Speed/Freq. in freespace or vacuum, though the same calculation always applied within the atmosphere, so any speed difference must have been negligible.
It worked out quite well in practice though there were other variable factors such as the type of antenna used and an average 5% reduction to allow for speed through the cable on HF, though this varied on other bands.