Notably used for communication with submarines, so in particular crucial as part of sending an attack signal to that branch of the nuclear triad.
This is likely the easiest one to produce as the frequencies are lower, which is why it was discovered first. TODO original setup.
Also because it is transparent to brick and glass, (though not metal) it becomes good for telecommunication.
Some notable subranges:
Micro means "small wavelength compared to radio waves", not micron-sized.
Microwave production and detection is incredibly important in many modern applications:
Microwave only found applications into the 1940s and 1950s, much later than radio, because good enough sources were harder to develop.
One notable development was the cavity magnetron in 1940, which was the basis for the original radar systems of World War II.
Apparently, DC current comes in, and microwaves come out.
TODO: sample power efficiently of this conversion and output spectrum of this conversion on some cheap device we can buy today.
Video 1.
Magnetron, How does it work? by Lesics (2020)
. Source.
Finance is a cancer of society. But I have to admit it, it's kind of cool. The secret world of microwave networks (2016) Fantastic article.
Video 1.
Lasers Transmit Market Data and Trade Execution by Anova Technologies (2014)
. Source. Their system is insane. It compensates in real time for wind movements of towers. They also have advanced building tracking for things that might cover line of sight.
Video 1.
How Microwaves Work by National MagLab (2017)
. Source. A bit meh. Does not mention the word cavity magnetron!
Video 2.
How a Microwave Oven Works by EngineerGuy
. Source. Cool demonstration of the standing waves in the cavity with cheese!
420 to 680 nm for sure, but larger ranges are observable in laboratory conditions.
Figure 1.
Toshiba D-088 dental X-ray tube
. Source.
Video 1.
William Coolidge explains medical imaging and X-rays (1940).
. Source. Video sponsored by General Electric. A cool insight of this video is that a hot cathode is a more reliable electron source. Previous systems, and presumably including the discovery of X-rays, leftover gas in the tube was used. But this makes things more difficult to control, as we also want to remove as much gas as possible from the vacuum, otherwise electrons collide with the gas and lose energy before hitting the anode.
Video 2.
How Does X ray Tube Works by BiomedEngg
. Source. Describes in particular the rotating cathode method. Interesting observation that this is especially important since the cathode cannot cool quickly due to the vacuum.

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