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In this experiment, learners construct an equilateral triangle using graph paper, a pencil, protractor and ruler. They also make a "laser triangle" using a laser pointer and front-silvered mirrors. Learners can use the geometric properties of an equilateral triangle combined with their understanding of the Law of Reflection to decide how to place the mirrors at each vertex so that the "laser triangle" fits their equilateral triangle. Learners also read about how Apollo astronauts helped scientists measure the distance to the Moon and the rate at which it's moving away from Earth by setting up special reflectors and lasers on the lunar surface.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
45 to 60 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 14 - 18

Resource Types:
Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Laser pointer
  • 1/2 inch binder clip
  • 8.5 x 11 inch graph paper
  • protractor
  • ruler
  • 3 front silvered mirrors
  • 3 CD jewel boxes to hold the mirrors in a vertical position (optional)


  • Earth and Space Science
    • Astronomy
      • Probes, Satellites and Spacecraft
    • Solar System
      • The Moon
  • Physical Sciences
    • Light and Optics
      • Lasers
      • Lenses and Mirrors
      • Reflection and Refraction
  • Engineering and Technology
    • Engineering
      • Aerospace Engineering
    • Technology
  • Mathematics
    • Geometry
    • Measurement
      • Polygons
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • 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