Set your first portal on the wall panel by the Light Bridge and then place the exit portal about halfway up the right-hand side of the wall panels on the left (over the pit). Press the red button and this’ll release a Cube that’ll bounce off of your suspended Light Bridge.
The problem is that the physics can sometimes mean that it can take several goes to get the Cube to land on the upper level (as you’ll see for yourself if you watch our solution video below).
Once you finally manage to snag a Cube, fire the Light Bridge portal on the upper right-hand wall (near the monitor) so it creates a barricade in front of the monitor. Now pick up the Cube and walk over the jump plate to get carried up to the upper level.
Turn to face the pit of turrets below and position the Light Bridge portal so it’s blocking the aim of all four turrets. Now pick the Cube back up and drop down to the ground floor where the switch resides. Set the Cube on the switch and immediately back away into the left-hand corner.
Place a portal on the wall directly in front of you and then another one on the wall panel directly above you. Step through and you can now make your way through the exit and to the next test chamber.