Player 2 : Once the light bridge has been positioned so it's directly under the funnel, stand underneath this funnel and once player 1 hits the red plunger, catch the ball as it drops down. Now join player 1 and head back onto the permanent light bridge.
Player 1 : Remove the portal from under the funnel, and set it so it takes you back to the entrance to the test chamber.
Player 1 : Carry the weight across the light bridge, drop down towards the circular resting place for the weight and drop it in to open the panels to the second part of this chamber.
Player 2 : Fire your first portal on the right-hand wall where the light bridge nears the exit area, and then place a second portal on the far right-hand side of the ceiling. This will create a vertical light bridge barrier, that'll travel down into the water.