Super Gelatin

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Can gelatin (like Jell-O ®) change the speed of light? Learners investigate the refraction properties of gelatin to calculate its index of refraction and discover that as the light travels through the gelatin, its speed and wavelength also change. This activity offers learners a challenge to find the index of refraction of an everyday, intriguing, translucent substance outside the standard listing of materials and refraction indexes.

Quick Guide

Preparation Time:
2 to 4 hours

Learning Time:
1 to 2 hours

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 14 - 18

Resource Types:
Activity, Experiment/Lab Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Wax paper sheets
  • Graph paper (1/4 inch ruled with blue ink)
  • Protractors
  • Scientific calculators (like a TI-30)
  • Protractors
  • Laser pointers
  • Binder clips big enough to grip the laser pointer and hold down the “on” switch.
  • Knox gelatin (8 x 7 ounce envelopes)
  • Desert gelatin with sugar (like Jell-O®) in red (strawberry) and yellow (pineapple).
  • Cookie sheet (1/2 to 3/4 inch deep, smooth and non-stick surface) or brownie pan (8 x 8inches, 2 inches deep)
  • 3 gelatin pans, preferably 8 x 8 x 2 inch brownie pans
  • Measure cup with a 2-cup capacity
  • Cooking spray (like Pam®)
  • 2 packages of Knox® plain gelatin (4 envelopes per pack)
  • 1 package of red gelatin (Jell-O® strawberry works well). Not sugar free. 1 package of yellow gelatin (Jell-O® pineapple). Not sugar free.


  • Earth and Space Science
    • Astronomy
  • Physical Sciences
    • Light and Optics
      • Lasers
      • Reflection and Refraction
    • Vibration and Waves
      • Wave Properties
    • Motion and Forces
      • Momentum and Velocity
  • Mathematics
    • Algebra
      • Equations and Inequalities
      • Variables and Expressions
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
      • Data Representation
    • Geometry
      • Plane Geometry
    • Measurement
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results

Informal Categories

  • Food and Cooking


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Components that are part of this resource:

Includes alignment to state and/or national standards:

This resource is part of:

Access Rights:

  • Free access


  • The University of Texas McDonald Observatory


  • All rights reserved, The University of Texas McDonald Observatory, 2011