Researchers at the University of California, Santa Barbara, have developed a novel method for imaging objects beyond the line of sight, which they've named "Wiffract." This technique...
You just need to write it smaller than the Wi-Fi wavelength (about 60 nm) and you should be fine. If someone wants to read it, they have to use smaller wavelengths (i.e. higher frequencies), which means there’s a good chance that they will be blocked by your walls.
Edit: c/2.4 GHz ≈ 125 mm
I took the first value from Wikipedia, without thinking about it enough.
It’s all about the size. You can’t use an optical microscope to look at details smaller than the wavelength of visible light. You need an electron microscope for that. Similarly, a wifi camera can’t see details smaller that the wavelength.
If you made a camera that can see in 100 MHz radio waves, you could probably see mountains, rivers and houses, but anything smaller than 3 m would be nothing but blur.
You just need to write it smaller than the Wi-Fi wavelength (
about 60 nm) and you should be fine. If someone wants to read it, they have to use smaller wavelengths (i.e. higher frequencies), which means there’s a good chance that they will be blocked by your walls.Edit: c/2.4 GHz ≈ 125 mm I took the first value from Wikipedia, without thinking about it enough.
I think your fag packet calculation has got a power of ten wrong somewhere. Wi-fi is GHz so that would be on the order of centimetres I think.
Yes. Wifi is 2.4 GHz, speed of light is 0.3 Gm/s. Therefore one wavelength is 0.3/2.4 m/s/Hz = 12.5 cm
Or 0.001 football pitches
Yeah, you’re right. Writing it smaller than 12.5 cm should do it, which is entirely reasonable.
What if I use an awesome font like Comic Sans and round the faces like party balloons? Still visible?
It’s all about the size. You can’t use an optical microscope to look at details smaller than the wavelength of visible light. You need an electron microscope for that. Similarly, a wifi camera can’t see details smaller that the wavelength.
If you made a camera that can see in 100 MHz radio waves, you could probably see mountains, rivers and houses, but anything smaller than 3 m would be nothing but blur.