Questions tagged [antennas]
The interfaces between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. Antennas are essential components of all radio equipment.
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Does an EM wave "turn around" and go inside an open-ended tube?
I am struggling to resolve a thought experiment that deals with the behavior of an EM wave as it reaches the end of a tube.
Assume a wave starts out traveling along the outside of a copper tube. The ...
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”Heisenberg-like” uncertainty principle(s) for antennas?
In harmonic analysis, we have the (one-dimensional) uncertainty principle:
$$\left(\displaystyle\int\limits_{-\infty }^{\infty }x^{2}|f(x)|^{2} \, \mathrm dx\right)\left(\displaystyle\int\limits _{-\...
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Which Electric Field an Oscillating charge produces - Coulombic,Induced,Both? What field is experienced by test charge at zero crossing of $E$ & $B$?
In my textbook (page 275):
https://blogmedia.testbook.com/blog/wp-content/uploads/2022/04/physics-part-i-chapter-8-b20d7a00.pdf
and on Wikipedia:
https://en.wikipedia.org/wiki/File:...
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Do window screens block WiFi? [closed]
I'm thinking of putting a wifi satellite on a screened in porch outside, to cover my yard. The Internet seems to think that wire screens don't block wifi, but wifi has a wavelength of 2 inches or more,...
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I need some help for radar gun physics? [closed]
I am doing a report on radar gun physics; it's for my high school physics report, so I don't really understand the core electrical physics well. I have read that the microwaves are produced by a Gunn ...
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A question re the mesh size, in an optical screen
Empirically, we know that a mesh screen to block EM waves, must have mesh size much smaller than the wavelength. e.g. microwave oven
What I find perplexing, intuitively, is the geometry underlying ...
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How dipole antenna radiate electromagnetic radiation?
I was reading about how accelerated cahrges radiate electromagnetic waves, and i found the most known application on it was the dipole antenna, which was by applying an alternating voltage signal the ...
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Slit diffraction experiment in the near field of an antenna
Diffraction Pattern in Near-Field vs Far-Field:
Consider a monochromatic EM wave with a wavelength of 3 km, produced by an antenna. Now, imagine placing a slit of 5 meters aperture at two different ...
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"Light faster than light" An interesting EM theoretic physics experiment in the near field region [closed]
Lets say we have an emitter antenna which produces an EM signal with a massive wavelength (300km), we have a receiver antenna 200km away form the emitter. We turn on the antenna, and when the ...
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Why do electromagnetic waves decay with $1/r$ when the fields they represent decay with $1/r^3$ and $1/r^2$?
When a change in voltage changes the static and inductive fields around an antenna, the change is propagated through space at the speed of light. Before the change arrives at a point in space, the ...
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Photon multiple wavelength antenna
Since light is an electromagnetic wave,
is it possible to build an antenna to receive many different frequencies?
From KHz to THz?
Or the wavelength makes it impossible?
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Can a microwave antenna detect single microwave photons?
In a lecture about satellite sounding our professor explained how microwave radiance is measured typically on satellites: There is an antenna behind a parabolic mirror and the received signal is ...
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How do antennas catch the correct radio signal in the air? [duplicate]
Radio signals come to antennas from certain directions. How does the antenna process of receiving the signal in the air work? How does a certain antenna receive this electromagnetic field as the radio ...
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Why length of antenna is $\lambda/4$?
I have read in my book under communication systems topic that the minimum length of antenna required for communication is wavelength/4 without any explanation. What is the reason for this? Why is only ...
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The 3.7 m dish antenna of Voyager
I need to know how Voyager-I was able to communicate with the base station on earth using the 3.7m dish antenna? Usually any dish antenna needs to be pointed towards the receiver and Voyager must be ...
