A spherical flask filled with high-index liquid simulates a large water droplet and projects a beautiful rainbow on a white cardboard screen when colimated white light is shined at it. This setup (shown to the left) is home-made, but the idea is copied from the UCB Physics Lecture Demonstrations catalog. A detail image of the rainbow is shown above.

To demonstrate the reflection and refraction inside of a water droplet we use a laser and 6L round flask filled with water.

List of Parts:

• Carbon arc lamp on a jack
• Framed cardboard screen (white on one side and black on the other) with a 50mm round hole in the center
• 100 mL round flask filled with Ethyl Cinnamate clamped to a stand
• 6L round flask filled with water with a bit of colloidal silver.
• Red or green laser on stand

Note: Position the flask between the light source and the students.