Sunlight experiment

Sunlight experiment

Inspire your kids to learn about the wonders of nature and how science can help explain amazing things like sunlight. This simple experiment can open their eyes to new ideas as you explore the properties of light together.

What you need:

  • Two plastic glasses
  • Tonic water
  • Tap water
  • Marker
  • Black paper or cloth

Number of players:


Line up two plastic glasses.

Fill one glass with tonic water, label it Tonic.

Fill the other with tap water, label it Water.

Place the glasses on the window sill or doorway where they are in direct sunlight.

Wait a moment before placing the black paper behind both glasses.

Look through the sides of the glasses for differences in colour on the surface of the two liquids.

You should see a blue fluorescence on the surface of the tonic water. This is due to the sun’s ultra-violet light filtering through the water.

Tonic water has quinine in it. Regardless of the time of day, when ultra-violet light is absorbed by quinine it emits a blue fluorescence, which is what you can see on the surface of the tonic water.

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