OK. I finally found the reason behind the problem. My wireless card was not working because I had never configured it. During the installation of the OS I had skipped the wireless card configuration process.
So the solution is to configure the wireless card while installation.
After the complete installation, while connecting to the access point, I encountered a problem, which I like to discuss, along with the solution.
Initially, the card is on off state. To wake it up, we type
ifconfig interface_name up
Where "interface_name" is the name of your wireless card. For different systems, the name varies. To get the name for your system, type
You may encounter an error "Error:Operation not possible due to RF-Kill"
This is because your wireless card is been disabled externally.To overcome this error, without typing any other command press the WIFI button your keyboard. After you press the button, type
ifconfig interface_name up again. Your Wifi will be in active state.
To connect to available networks follow this link