It is possible to power a device with radio waves - the most basic crystal radio just drives a speaker using the acquired radio signal. In 1945 the USSR “gifted” a concealed listening device (The Thing) to the US ambassador which worked this way - it was only “on” when an external radio was transmitting the correct frequency, making it very hard to detect. RFID tags also work the same - they don’t require batteries because the chip is activated when the tag’s antenna gets hit by the radio from the scanner.
This is only practical for very low-power devices, because transmitting high-power radio waves is dangerous.
Ah, no. Electromagnetic induction and electromagnetic radiation are related but different - induction doesn’t produce radiation (radio) waves that would travel longer distances.
It is possible to power a device with radio waves - the most basic crystal radio just drives a speaker using the acquired radio signal. In 1945 the USSR “gifted” a concealed listening device (The Thing) to the US ambassador which worked this way - it was only “on” when an external radio was transmitting the correct frequency, making it very hard to detect. RFID tags also work the same - they don’t require batteries because the chip is activated when the tag’s antenna gets hit by the radio from the scanner.
This is only practical for very low-power devices, because transmitting high-power radio waves is dangerous.
It would likely be sufficient for things like smart wearables, though. Maybe even smart watches