This asked: What is the minimum wavelength of electromagnetic radiation?
And also this: What is the maximum possible frequency and wavelength?
The second question is contradictory; maximum frequency -> minimum wavelength.
I am asking the very opposite;
What is the minimum frequency and maximum wavelenght of electromagnetic radiation?
The lowest measured/defined seems to be 3 Hz; ELF-waves Which means a wavelenght 1/3 of the speed of light; ~100 000 000 m.
But this can't be the physical limit for the wavelenght.
Does such a physical limit for the wavelength exist? (Similar limit like the speed of light is for velocity).
Answer
There is no theoretical physical limit on the wavelength, though there are some practical limits on the generation of very long wavelengths and their detection.
To generate a long wavelength requires an aerial of roughly one wavelength in size. The accelerated expansion of the universe due to dark energy means the size of the observable universe is tending to a constant, and that will presumably make it hard to generate any wavelengths longer than this size.
As for detection, we tend to measure the change in the electric field associated with an EM wave not its absolute value. As frequencies get lower we will need either increased intensity waves or ever more sensitive equipment. Both of these have practical limits, though I hesitate to speculate what they are.
No comments:
Post a Comment