try this from terminal (execute bellow commands with order) (Active Internet connection required)
Reboot your PC and remove the Ethernet Cable. See if wireless works.
sudo apt-get purge bcmwl-kernel-source
sudo apt-get install firmware-b43-installer
echo 'b43' | sudo tee -a /etc/modules
Or else give the results of below commands
When I said "Put the results between the brackets"
dmesg | grep -ie b43 -ie firm -ie net
I mean to put the results between these brackets ==> [CODE]the results here[/CODE] <=== so the results displayed OR
you can click the "New Reply" and highlight the results and click this symbol # at the message toolbar.