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    The Exploratorium

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In this activity, learners explore their eye pupils and how they change. Learners use a magnifying glass, mirror, and flashlight to observe how their pupil changes size in response to changes in lighting. Learners also experiment to determine how light shining in one eye affects the size of the pupil in their other eye. This resource guide includes background information about pupils and why they change as well as information related to emotional stimuli, involuntary reflexes, and photography.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:

Age Range:
Ages 8 - 14

Resource Type:


Materials List (per student)

  • A magnifying glass (at least 1 inch [2.5 cm] in diameter)
  • A mirror (a small, flat, compact mirror, a plastic mirror 4 x 4 inches [10 x 10 cm] or larger, or a wall mirror)
  • A flashlight
  • Eyes


  • Life Sciences
    • Human Body
      • The Brain and Nervous System
    • Human Senses and Perception
      • Vision
      • Perception
  • Physical Sciences
    • Light and Optics
      • Lenses and Mirrors
      • Reflection and Refraction

Informal Categories

  • Photography and Film/Video


To use this activity, learners need to:

  • see
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access



  • All Rights Reserved, The Exploratorium,

Funding Sources:

  • National Science Foundation
  • California Department of Education
  • NEC Foundation of America


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