Total Internal Reflection

Total internal reflection can occur when light is in a material that is more dense than its surrounding. Light incident on the internal surface at certain larger angles will reflect back into the material with no light escaping (no light refracting out). This is the foundation to fiber optics (now often used in communication transmission). The incident angle at which light just escapes (refracted angle of 90 degrees) is the called the critical angle.

Experiment

• With the half circle solid plastic, see if you are able to observe total internal reflection by shining the laser into the plastic on the circular part (and observing the internal reflection from the planer part). Determine the critical angle for total internal reflection in the plastic.