Touch the Spring (Lightbulb)

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In this activity, a lightbulb is placed in front of a concave mirror. The actual lightbulb is not visible to the viewer, but the viewer can see the mirror image of the lightbulb formed in space. When the viewer tries to touch the lightbulb, they are attempting to touch an image. Their hand moves right through what seems to be a solid object! Learners will enjoy this illusion, while investigating principles of light and mirrors. In this version of a popular Exploratorium exhibit, a lightbulb is substituted for a spring.

Quick Guide

Preparation Time:
45 to 60 minutes

Learning Time:
30 to 45 minutes

Estimated Materials Cost:
Over $20 per group of students

Age Range:
Ages 8 - 14

Resource Types:
Activity, Demonstration, Exhibit


Materials List (per group of students)

  • A 16 inch (40 cm) diameter concave mirror
  • Wood to build a support stand for the mirror and a small box for the lightbulb. (See photo and drawings.)
  • 2 light sockets, one with an electrical cord and plug
  • A lightbulb, 40 to 75 watts
  • One 3 x 5 inch (8 x 13 cm) card
  • Adult help


  • Life Sciences
    • Human Body
      • The Brain and Nervous System
    • Human Senses and Perception
      • Vision
      • Perception
  • Mathematics
    • Geometry
      • Plane Geometry
  • Physical Sciences
    • Vibration and Waves
      • Light and Optics
    • Light and Optics
      • Lenses and Mirrors
      • Reflection and Refraction
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • be mobile
  • 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



Funding Sources:

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