15. A ray of monochromatic light travelling in air strikes the end of a 21 cm wide block of Plexiglas at an incident angle of 65. The index of refraction for the Plexiglas is 1.51 and for air is 1.003. The light travels to the opposite side of the block and refracts out into the air. The path of the retracted light ray is parallel to the original light ray but displaced a distance d. Calculate the value of d. Draw diagram