Mathematics and Society - OS X Lion Server

BENDING OF LIGHl=(7[(?1?l[rIL7NWhen light passes from one tranSparentmaterial into another its speed changes.If the light hits obliquely this change ofspeed will be seen as a bend in the lightray at the boundary. This phenomena isknown as refraction.i IS T~E I\.lCIDEfJT ANGLE, MEA'SUREDBETWEEN T\.it:. IMCIDEl\IT RAY AND THe.PE:RPEIUOICUl.AR AI Tf1E POll\lT WHERE'THE IIUCIDEl\lT RPN It-lTERSECTS THE:.GLA'?,S.Several classroom demonstrations of refraction aresuggested below.I Put a pencil obliquely into a glass of water. Therefraction of light at the boundary of the air andwater will give the illusion that the pencil isbroken.IIPlace a coin on the bottomof a metal pan. Have studentsback up so the lipof the pan just hides theCOlt-!coin. With students stayingexactly the same position slowly add water. As the water level rises thecoin will become visible.III Give students a glass prism or rectangular piece of plastic or glass and havethem place it on a picture. As they tip the prism forward and back the pictureseems to move under the glass.The ratio of the speed of light in a vacuum to the speed of light in any otherparticular transparent material will give a constant value.of refraction (N).speed of light in a vacuumspeed of light in water1. 33 = N (water)speed of light in a vacuumspeed f I ' h 'd' d = 2.42 = N (diamond)0 ~g t ~n ~amonThe index of refraction of air is 1.00It is called the index367