Why does an Android phone show the WiFi icon for a few seconds even after the router's turned off?

[kethsusarla]

I was browsing on my phone today and the power went off. I could still see the WiFi icon active with my network name.
I think it's just a delay in the OS's process to update the display. My room-mate on the other hand argues that it's because of the radio waves that are still in the air even when the source's been turned off.
I use an Android phone (OnePlus 2).

 

[AlphaTango414]

I'd say it's probably a little of both but more the OS just being delayed. Look at how long it takes some devices to toggle off wifi.