Protractor - Law of Reflection (Laura Silverman)



Author

          Laura Silverman, 7th grade Science, Mulholland Middle School

Principles

The angle of reflection is equal to the angle of incidence.

Standards

Physical Principles in Living Systems (Physical Sciences)

    7.6. Physical principles underlie biological structures and functions.

    g. Students know the angle of reflection of a light beam is equal to the angle of inci­dence.

Materials needed

paper protractor

sheet protector

small mirror with flat edge (no border)

maglight (the smaller the better)

Procedure

Have students pick an angle of incidence, then demonstrate that the angle will be the same at the other side.

Explanation

The mirror provides a perfect reflection and bounces the light at an equal angle from the normal line drawn perpendicular to the mirror edge.

Questions

  1. What is the angle of the incident light from the flashlight to the mirror?
  2. What is the angle reading on protractor from the reflection from the mirror?
  3. Are these angles the same?

Everyday examples of the principles illustrated

Light bounces off mirrors in solar panels and in telescopes.  Also you can see sunlght reflecting from car windows, building windows, and other reflective surfaces.

Photos

reflection from mirror

reflection with protractor

reflection with writing

Movies

Here is a more elaborate set up using a light box to generate the light beam.

References

Here is a website of this lab from the College of Micronesia:
CS 130 Angle of Reflection

Here is another site from University of South Carolina
Lab 2 Reflection of Light



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