Glowing Tonic

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In this sunny day activity, learners compare how a cup of water and a cup of tonic water reflect or refract light in the sun. Learners will be surprised to observe the top of the tonic water "glowing" blue. This activity includes articles explaining the reflection and refraction of light.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
5 to 10 minutes

Estimated Materials Cost:
$1 - $5 per student

Age Range:
Ages 6 - 11

Resource Type:


Materials List (per student)

  • 2 clear plastic cups
  • 1 liter of tonic water
  • Tap water (enough to fill 1 cup)
  • Permanent marker
  • Black paper or felt
  • Clear plastic
  • Sunny day


  • Physical Sciences
    • Vibration and Waves
      • Light and Optics
    • Light and Optics
      • Reflection and Refraction
      • Sunlight and Color
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Food and Cooking
  • Outdoor Activity


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access



  • All rights reserved, Optical Society of America, 2008