Brightness problem in Ubuntu 11.04

i was unable to change brightness in ubuntu 11.04 operating system. so i googled (google it) the problem and i come up with one common solutions over the internet.

here it is,
1) go to terminal.

2)enter following command for low brightness

echo 0> /sys/class/backlight/acpi_video0/brightness

3)enter following command for high brightness

echo 6 > /sys/class/backlight/acpi_video0/brightness

i m not 100% sure that it will work for you. at least you can give it a try. :D