6A44.45-Laser Waterfall

Description: This demonstration shows total internal reflection through a stream of water.

Equipment:

• Laser
• Jack stand
• Laser waterfall container
• Powdered milk
• Water
• (Optional) Pyrex beaker
• (Optional) Red food coloring

Setup Procedure:

1. With the cork in, fill the container up with water.
2. Mix in a small amount of powdered milk.
3. Place the container on an extended jack stand. Position it so it aims at the sink.
4. Aim the laser straight through the container at the cork.
5. (Optional) Fill a Pyrex beaker full of water, add a drop of red food coloring, and place it in the sink without students seeing.

Demonstration Procedure:

1. Turn on the laser. Double check to make sure it’s lined up on the cork.
2. Turn off the lights.
3. Pull the cork plug out.
4. Note that the laser beam travels in the stream of water. This is due to the laser light exhibiting total internal reflection.
5. Turn of the laser.
6. (Optional) Pull up the beaker with red food coloring. You can say you trapped all the laser light.

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