I think that the best way to perform the test is to have the sloping wall adjustable, because it probably is a bit of a push to get the photon around the corner. I would also put Kodak paper there just to see where the photon is hitting for the first few tests. Maybe I would make a sliding slit too, to get that right. What should happen is that the first few photons will hit the atoms in the slope. The atoms should then break the bubbles around the slope turning them into a denser material. This should then cushion the next few photons around the bend.