[OT] Wireless internet in my flat.

[Richmond]

I have a wired+wireless router connected to my cable modem in my flat.

My Dell Optiplex 745 running Linux is connected via a LAN cable to the 
router.

My G3 iMac running Mac OS 9.2.2 is connected via LAN cable.

My G5 iMac running Mac OS 10.4 and 10.5 connects wirelessly.

My wife's laptop (generic rubbish) running Linux connects wirelessly.

My iPad 1 connects wirelessly.

My wife's Android NextBook connects wirelessly.

My wife's Dell Optiplex 760 with wireless dongle connects wirelessly.

My older son's iPad 4 connects wirelessly.

Both of my sons' iPhones connects wirelessly.

My older son's Lenovo laptop running Windows 7 connects wirelessly.

BUT . . . My younger son's MacBook Air running Mac OS 10.10 is UNABLE to 
connect wirelessly . . .

Would be glad for any pointers as to why.

Richmond.