Should the beam of light will not be orthogonal (or rather standard) to your boundary, the change in wavelength results in a adjust in the route with the beam. This variation of direction is known as refraction. John LawlerJohn Lawler 109k1111 gold badges185185 silver badges489489 bronze badges three one https://eduardo60p03.targetblogs.com/37007337/considerations-to-know-about-bedspreads