herein by setting up an experiment such as illustrated in fig4 here the student places beam collimator 21 over the center of lens 22 of light projector 23 and secures the collimator to the lens by using a fastening material such as cellophane tape a protractor 24 is then placed on elevated surface 25 closely spaced to the light projector thereafter the student secures a flat mirror 26 substantially perpendicular to surface 25 and employs masking tape to cover the mirror and place an approximate 2 millimeter verticle slit 27 at the center of the mirror the student then places mirror 26 on protractor 24 so that slit 27 is directly over the meeting point of the protractor and the plane of the mirror is precisely along the base line thereafter the student turns on the projector and adjusts the lens assembly until the narrow ray of light is directly on the narrow slit of the mirror the light from the projector crosses the protractor at a specific angle which is measurable as shown in fig4 the student can measure the angle of incidence by measuring the angle formed by the ray of light and the 90 u00b0 line on the protractor in a likewise manner the student can measure the angle of reflection by observing the.