Part IV. Total internal reflection 1. Now choose oil for the top layer and now water for the bottom layer. Click " Go" at the top left to fire the laser. 2. With the protactor enabled, move the laser (click and drag it) within the upper layer to carry out a refraction experiment for several incident angles i . Measure the angles i and r. 3. Find the angle at which there ceases to be any refracted beam. This is the angle of total internal reflection