A. Snell's Law AP-1. Measure the angle of incidence and the angle of refraction for the semi-circular Lucite disk. The best way to do this, as depicted in Figure 16.5, is to use a semi-rectangular plastic bottle, shaped like e (the canted-neck bottle is actually a discarded cell culture suspension flask from a biological laboratory experiment) to trace the path of the incident ray through the air. In order to see the laser beams better, you may need to request that the room lights be turned off. You will find it easier to measure the complementary angle, , rather than . CAUTION: Do not move the laser or Lucite block during the time between making the incident and refracted beam measurements. First, use the ruler to find the middle of the rectangular side of the Lucite semi-disk and draw a line through this so that it intersects with the centers of the circles that form the two semi-circular faces. Next, place the lateral side of the plastic bottle directly against the flat face of the semi-disk. Let the laser beam enter the plastic bottle at the angled side near the mouth of the bottle and aim it at the line marking the center of the rectangular side of the semi-disk. If done correctly, the refracted beam trajectory through the semi-disk should coincide with a radius from the center of the circle such that the beam emerges along the curved side of the semi-disk perpendicular to that surface. Using the erasable marker pen, mark the points on the bottle and the semi-disk where the beams traverse the interfaces. The ruler can be used to draw straight lines across the top faces of the bottle and semi-disk joining the marked points on the interfaces. Finally, one can measure the respective complementary angles using the protractor. AP-2. Place the triangular glass plate (effectively, a two- dimensional prism) on top of the rectangular Lucite block and position them against the Lucite semi-disk, forming a glass-Lucite interface as shown in Figure 16.6. Shine the laser beam through the glass into the Lucite as shown in Figure 16.6 and measure whether the beam is bent like Path A or Path B as shown. One case (A or B) will occur if Lucite has an Index of Refraction, nructe that is larger than that of glass, nglass. The other case (B or A) corresponds to npucite