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Law of Reflection
AKA: Plane Mirror Reflections


Experiment to show the laws of reflection using a plane mirror and raybox.


This practical can be conducted as a demonstration or as a class experiment. The main aim of the lesson is for students to demonstrate and understand the laws of reflection using some simple equipment.

Equipment required (per set):

  • Raybox and slit
  • Power supply for raybox
  • Optics screen
  • Plane mirror and holder
  • Protractor
  • White paper

The plane mirror should be stood up using a stand, facing the raybox. A single slit is placed in the raybox and the single beam pointed towards the mirror. Other lamps may be used instead of a raybox for this practical (such as a slide projectot) as long as the beam projected is thin and bright. Alternatively for a teacher demonstration, a laser may be used.

A line is drawn on the paper at 90° from the centre of the mirror, this is known as the normal. When a single beam is projected from the raybox, the angle between this ray and the normal is called the angle of incidence. The angle between the normal and the ray reflected back off of the mirror is called the angle of reflection.

Be aware that rayboxes may remain hot long after use.

The optics screen can be constructed before the lesson if needed. Details can be found in our Workshop section, see the links below for this and other related pages.


 CautionThe contents of this page are for information only. Please refer to CLEAPSS, SSERC or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.