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This is an excellent question, that deserves a more thoughtful answer (no offense guys). The question that Unknown is asking (I think) is why should there be a node or antinode at each end of a cylinder? When the end is closed, it is fairly easy to see that the air cannot move any further along, so the displacement of the air will be zero - in other ...

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You are basically correct. An air-filled cylinder that's open on both ends will actually resonate at multiple resonant frequencies, given by $$f=\frac{n v}{2L}$$ where $n$ is a positive integer, $L$ is the length of the tube, and $v$ is the speed of sound in air. The fundamental frequency, which generally contains the most energy, is the case when $n=1$, ...

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Depends on the ends of the tube: An open end is a displacement anti-node (unrestricted), a closed end is a displacement node (restricted). Thus, a tube that is open at one end and closed at the other will have natural frequency and harmonics such that there is a node on the closed end and anti-node on the open end (a quarter wavelength). If both ends are ...

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The requirements for transmitting antennae are much higher than for receiving antennas. Transmitting antennas must optimally radiate, so that the signal is not obscured by other stations with better antennas. If an receiver antenna to short and far away from resonance, all received stations are uniformly weaker. What matters is that the desired signal is not ...

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"Bright light can never hurt your eyes" seems false to me… enough energy focused on the retina will cause damage, regardless of the wavelength. Otherwise you would not need to wear laser goggles… That aside, materials typically have certain ranges where they absorb light more strongly than others. There is no hard and fast rule for this, but if you google ...

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Uv goes thru glass, I thought that comment strange when I watched it. Laminated glass (which it could have been) would shield about 95% of the uv, I believe due to the resin interlayer.

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The lowest frequency limit is provided by the size of the universe. If we could make an antenna that size, the frequency would be "very close" to zero. The highest EM frequency limit is provided by the smallest antenna we could make. I believe that would be the size of a hydrogen atom, giving us, F_u = \frac{2.997x10^8}{6.28x5.29x\$10^{-11}} = ...

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