Tell me more ×  Near Field Communication (NFC) operates at 13.56
MHz.  Near Field is the region situated at a distance r << λ  λ
= c/f  c = 299 792 458 m/s in the vacuum. f = 13.56 MHz =
10.56*10^6 Hz  λ = 22.11 m  Of this distance, the Reactive Near
field is commonly considered λ/2π. For NFC, this would be 3.51
m.  So where do the 20 cm come from?  share|improve this
question I think it's better suited for electronics.SE, but see
my answer below. –  Sigrlami Nov 12 '12 at 20:44 @Sigrlami You
might be right. I didn't know there was an electronics SE. If
any moderator wants to migrate the question I'm fine with it. – 
Mister Smith Nov 13 '12 at 8:33 Technically physics support
almost every engineering discipline.=) FAQ says: Physics Stack
Exchange is for active researchers, academics and students of
physics and astronomy. As for me, your question stands on the
edge between physics and electronics. –  Sigrlami Nov 13 '12 at
10:08 I think that this question is a good fit here on Physics
(look at the detail on an