Reflection by a plane mirror

Principle

The aim of this experiment is to experimentally determine the laws of reflection.
 
In doing so, we deliberately refrain from introducing the terms "angle of incidence", "normal to the reflecting surface" and "angle of reflection" to begin with. In the course of the experiment the students become acquainted with these terms which are appropriate for the unequivocal determination of the investigated quantities. However, the students should be told before beginning the experiment that it is helpful to measure angles and to compare them to investigate the correlation between the direction of the incident and the reflected light beam.
 
The experiment consists of two parts.
 
In the first part the angular dependency of reflection is investigated on a plane mirror, and the law of reflection with its statements concerning angle of incidence and angle of reflection is determined.
 
In the second part of the experiment the students indirectly prove that the incident and reflected beams of light and the normal to the reflecting surface all lie in the same plane. By changing the position of one half of a sheet of paper, it is shown that only when both halves of the sheet are in the same plane is the reflected light beam visible in its entire length.
 
Thus, the two partial experiments form a unit in terms of the comprehensive experimental determination of the law of reflection; however, they can also be conducted separately. Similarly, a differentiated application in a group of students or a complete omission of the experimental determination of the positional relationships is possible.

Benefits

• Multifunctional light box - All-in-one: Can be used for geometric optics on the table, colour mixing and on an optical bench
• Extension with others sets at anytime, no additional light sources needed, recognition value for students

Tasks

How can you look around the corner of a house with a mirror? In this experiment, the connection between the mirror's incident and reflected light beam is investigated. In a second step it is determined how to hold a piece of paper to see the reflected light beam in its entire length.