The Electromagnetic Spectrum
Light, Sound and Waves

Eerie Blue Water

Enrichment Activity for 5-11 11-14

What you need

  • Two clear glasses
  • Tap water
  • Tonic water
  • Dark paper


  1. Fill one glass with tap water and the other with tonic water and put them both in direct sunlight
  2. Holding the dark paper behind them, but not blocking the light, look across the surfaces of the water

Results and Explanation

The tonic water will be giving off an eerie blue glow! Tonic water contains quinine. The quinine absorbs ultraviolet light from the Sun and re-emits it as visible blue light.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

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