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General Science / Re: Fans Are So Shallow, I can see right through them !!
« on: 15/07/2020 09:22:37 »
- The fact that you do not see the rotor spinning is an other case of what is illustrated by a test everyone must have seen in physics class : a circular disk is divided in seven or 14 sectors, each showing an other colour of the rainbow. When you make the disk spin, you do not see the different colours but just gray. So in this case you do not see the different wings but you do see what shows up repeatedly behind them
- You can see the fan spinning if you use a stroboscope. If the frequency of the flashes is synchronized with the speed of your fan, it will look as if the fan stands still, if the frequency is marginally lower, you'll see the fan turning forwards, if the frequency is higher it will turn backwards. A single TL-tube will have the same effect, but since you can not change its frequency, you would have to change the speed of the fan. (Twin tube ornaments will have the tubes arranged in such a way that one is on while the other is off and vice versa, so no stroboscopic effect.)
And concerning that other point : you feel colder because the blast of air helps your transpiration evaporate, which requires energy.
This brings me to another question: Can we confuse a snake or a mosquito using a fan because they see heat instead of images?