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In this activity about light and perception, learners discover how a flash of light can create a lingering image called an "afterimage" on the retina of the eye. Learners will be surprised when they continue to see an image of a bright object after staring at it and looking away. Use this activity to introduce learners to principles of optics and perception as well as to explain why the full moon often appears larger when it is on the horizon than when it is overhead. This lesson guide also includes a few extensions like how to take "afterimage photographs."

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
1 cent - $1 per student

Age Range:
Ages 8 - 18

Resource Type:


Materials List (per student)

  • A flashlight
  • White paper
  • Opaque black tape (such as electrical tape)


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


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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