How do you get out of chamber 3?

Based on where you are standing in that screenshot, there should be an orange portal already in place to your right. You can only shoot blue portals so how would you get a portal on the other side so you can use the one that you can already reach?

Just shoot a blue portal to the other side and walk through the orange portal that is nearby.

The point of this test is teaching you that the two portals are functionally equivalent: you are not going to always enter the blue portal and leave the orange portal.

This time, you instead need to enter the orange portal and leave the blue portal by placing the blue portal by the door.