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Results tagged with electromagnetic-radiation
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user 1370
Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.
2
votes
Accepted
Magnetron limits
To produce higher frequencies by a magnetron, one needs
higher plate (anode) voltage and a stronger magnetic field,
to keep the electrons within the central cavity.
So, first limit is the magnet, if …
- 6,944
7
votes
Accepted
What determines how much light is reflected and refracted?
Look here:
http://en.wikipedia.org/wiki/Fresnel_equations
This is for transparent media, the formulas for metals are somewhat more complicated.
- 6,944
0
votes
Magnetic fields and gravitational waves. How far do they reach?
In this thread one point was not discussed yet,
as far as I read:
That "wire" (which everybody will assume to be straight)
is misleading. A wire with a battery makes a electric
ciruit! "Circuit" ha …
- 6,944
14
votes
Why do car keys have longer range when held next to your head?
It works with a lot of body parts. It will work with a piece of
wire too. This keys work at about 433 Mhz, a resonant Lamda/4 antenna
is about 18 cm. Obviously the whole key is shorter, the antanna …
- 6,944
9
votes
Accepted
How do laser rangefinders work when the object surface is not perpendicular to the laser beam?
so only a tiny fraction of beam energy
is reflected back to the device.
This tiny fraction is enough. With respect to ambient light:
One can modulate the laser beam, and filter the the voltage …
- 6,944
3
votes
Accepted
Is a superconductor perfectly opaque?
At the frequencies (=energy) of visible light, there is no superconductivity.
The band gap due to Cooper pairs is much smaller.
Radiation at higher frequencies (energies) breaks Cooper pairs, creatin …
- 6,944