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I apologise for my strange question :-) I suppose that when I turn on an wifi device it emit continuously radio wave. What happens when I turn off the device? The last wave emitted how long bounce in the room? Thanks

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  • Radio waves travel at the speed of light. How long does the light bounce around in the room after you turn the lamp off? This question probably belongs on Electrical Engineering. – Ron Maupin Dec 17 '17 at 23:00
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In a small room, say 3 m wide, with radio travelling very close to 300,000,000 m/s, it takes about 10 ns to cross the room. Each time it bounces off the wall it will be very much attenuated. Perhaps it takes five bounces before it's entirely insignificant, so that's about 50 ns. It's pretty brief.

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  • Ah ok, very interesting. :-) It's true that the wireless wave bounce also on the glass of the window? Someone told me that the 2.4GHz is opaque to the glass. – robyg72 Dec 18 '17 at 6:33
  • I know that windows can be pretty opaque to radio, especially double-glazed ones, whch are often coated and can be as much as 15dB in signal loss (ie, they let only about 3% through); some are only 3 dB (50%). I don't know the extent to which they are reflective versus absorbent. – jonathanjo Dec 18 '17 at 12:38

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