While I was trying to install Ubuntu, the wifi was working fine but after installation and update, I'm unable to connect to wifi. Can you please guide me on it.

Seeing other posts with similar description I've run lspci -nn and here are the results.

lspci -nn

00:00.0 Host bridge [0600]: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub [8086:2a40] (rev 07)

00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07)

00:02.1 Display controller [0380]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a43] (rev 07)

00:1a.0 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 [8086:2937] (rev 03)

00:1a.1 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 [8086:2938] (rev 03)

00:1a.2 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 [8086:2939] (rev 03)

00:1a.7 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 [8086:293c] (rev 03)

00:1b.0 Audio device [0403]: Intel Corporation 82801I (ICH9 Family) HD Audio Controller [8086:293e] (rev 03)

00:1c.0 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 [8086:2940] (rev 03)

00:1c.1 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 [8086:2942] (rev 03)

00:1c.3 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 4 [8086:2946] (rev 03)

00:1c.4 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 5 [8086:2948] (rev 03)

00:1c.5 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 6 [8086:294a] (rev 03)

00:1d.0 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 [8086:2934] (rev 03)

00:1d.1 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 [8086:2935] (rev 03)

00:1d.2 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 [8086:2936] (rev 03)

00:1d.7 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 [8086:293a] (rev 03)

00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev 93)

00:1f.0 ISA bridge [0601]: Intel Corporation ICH9M LPC Interface Controller [8086:2919] (rev 03)

00:1f.2 SATA controller [0106]: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] [8086:2929] (rev 03)

00:1f.3 SMBus [0c05]: Intel Corporation 82801I (ICH9 Family) SMBus Controller [8086:2930] (rev 03)

09:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168 PCI Express Gigabit Ethernet controller [10ec:8168] (rev 03)

0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01)

0f:00.0 SD Host controller [0805]: Ricoh Co Ltd MMC/SD Host Controller [1180:e822] (rev 01)

0f:00.1 System peripheral [0880]: Ricoh Co Ltd R5U2xx (R5U230 / R5U231 / R5U241) [Memory Stick Host Controller] [1180:e230] (rev 01)

0f:00.3 FireWire (IEEE 1394) [0c00]: Ricoh Co Ltd R5C832 PCIe IEEE 1394 Controller [1180:e832] (rev 01)