- #1
soup_
- 13
- 0
Ok, I'll try to make my question as clear as possible, but since the question arises from confusion, it may be difficult.
In an electromagnetic wave, what exactly is waving?
If the answer is field strength, then why do things like the size of the holes on the screen on a microwave oven, or the size of a radio antenna (how it should be proportional to wavelength) matter?
If the answer isn't field strength, then is something physically moving up and down? If so, what?
Back to the antenna idea. Let's say I have a dipole antenna that is vertically aligned and is one wavelength of whatever frequency I'm trying to transmit. This is often pictured as a cartoonish red or blue sinusoid emanating from the antenna with an amplitude of the height of the antenna. I have a feeling this is wrong, but let's assume it is accurate so someone can explain to me why it isn't. So for an antenna to emit this cartoonish sinusoidal wave, something in the metal is moving up and down sinusoidally that is spitting out blue pixels that travel parallel to each other away from the antenna at c.
Now suppose I have a receiving antenna a km away that is exactly the same size and same height from the ground. It would seem these blue pixels hit the metal and cause the appropriate voltage oscillations in the wires. But what if I move the antenna up or down by 10, 20 or 200 percent of it's length? This doesn't pose a problem. Well, I might lose a little bit of strength, but if you think about the cartoon, I'm completely missing the blue pixels. But if I chop of, say, 10% of the antenna, I'm basically screwed. I'm assuming that moving it up or down doesn't hurt because the sinusoid is not alone, but has many copies, some going out radially (like ripples from a stone thrown in a pond), but also some not coming out directly horizontally but some sinusoids flying towards the sky and some towards the ground. But copies don't make sense either, because wouldn't they then interfere with each other somehow? So is it that it isn't a stream of pixels but more like a pressure that forces something that is already present to move up and down (like ripples on a pond)? If so, what is it moving up and down?
And finally, if this is the case, why does changing the length of an antenna have such a great effect?
And again, if a whole huge chunk of the ether (or whatever) is moving up and down, what do the size of the holes in the microwave screen have to do with anything?
Thanks,
soup
In an electromagnetic wave, what exactly is waving?
If the answer is field strength, then why do things like the size of the holes on the screen on a microwave oven, or the size of a radio antenna (how it should be proportional to wavelength) matter?
If the answer isn't field strength, then is something physically moving up and down? If so, what?
Back to the antenna idea. Let's say I have a dipole antenna that is vertically aligned and is one wavelength of whatever frequency I'm trying to transmit. This is often pictured as a cartoonish red or blue sinusoid emanating from the antenna with an amplitude of the height of the antenna. I have a feeling this is wrong, but let's assume it is accurate so someone can explain to me why it isn't. So for an antenna to emit this cartoonish sinusoidal wave, something in the metal is moving up and down sinusoidally that is spitting out blue pixels that travel parallel to each other away from the antenna at c.
Now suppose I have a receiving antenna a km away that is exactly the same size and same height from the ground. It would seem these blue pixels hit the metal and cause the appropriate voltage oscillations in the wires. But what if I move the antenna up or down by 10, 20 or 200 percent of it's length? This doesn't pose a problem. Well, I might lose a little bit of strength, but if you think about the cartoon, I'm completely missing the blue pixels. But if I chop of, say, 10% of the antenna, I'm basically screwed. I'm assuming that moving it up or down doesn't hurt because the sinusoid is not alone, but has many copies, some going out radially (like ripples from a stone thrown in a pond), but also some not coming out directly horizontally but some sinusoids flying towards the sky and some towards the ground. But copies don't make sense either, because wouldn't they then interfere with each other somehow? So is it that it isn't a stream of pixels but more like a pressure that forces something that is already present to move up and down (like ripples on a pond)? If so, what is it moving up and down?
And finally, if this is the case, why does changing the length of an antenna have such a great effect?
And again, if a whole huge chunk of the ether (or whatever) is moving up and down, what do the size of the holes in the microwave screen have to do with anything?
Thanks,
soup