What You Did
You simulated a fiber optic cable with a stream of water.
Intended Results
When you removed the tape, some of the light bent as it followed the stream of water out of the bottle rather than shining straight through it as normal.Making the hole bigger makes more of the light bend as more photons get caught in the stream of water.
Unintended Results
Using a weak flashlight will make for a less brilliant effect.
Keep Tinkering
Try making the hole even bigger. Compare different colors of light
Explored Concepts
fiber optics, electromagnetism, communication systems