<p> Refraction, Snell’s Law, and Total Internal Reflection</p><p>1) Why do clear streams look so shallow? 2) Suppose you are lying on the bottom of a swimming pool looking up at a ball that is suspended 1 meter above the surface of the water. Does the ball appear to be closer, farther away, or still 1 meter above the surface? 3) A ray of light enters the top of a glass of water at an angle of 36 degrees with the vertical. What is the angle between the refracted ray and the vertical? 4) The angles of incidence and refraction for light going from air into a material with a higher index of refraction are 63.5 degrees and 42.9 degrees, respectively. What is the index of refraction of this material? 5) A person shines a light at a friend who is underwater. If the ray in the water makes an angle of 36.2 degrees with the normal, what is the angle of incidence? 6) Calculate the critical angle for light going from glycerine into air. 7) A fiber-optic cable has an index of refraction of 1.53. For total internal reflection, what is the minimum angle of incidence to the inside wall of the cable if the cable is in the following: a. Air b. Water</p><p>Snell’s Law: N(in)sine(angle in) = N(out)sine(angle out) ** Always measure the angle (in degrees) from the line perpendicular to the surface N = index of refraction = speed of light in air/speed of light in other material. N is greater than or equal to 1.0</p><p>Index of refraction (N) for a few materials N(air or vacuum) = 1.0 N(water) = 1.33 N(glycerine) = 1.47 N(Glass)= 1.5 N(diamond) = 2.42</p><p>Total Internal Reflection happens only when light travels from a “slower” material to a “faster” material (from a material with higher index of refraction to a lower index of refraction). The light can’t “escape” at the surface. The Critical angle is the incident (or in angle) where the refracted (or out) angle = 90 degrees. </p><p>Answers: 1) Light refracts, making objects appear shallower, draw a picture. 2) Light refracts, makes the ball appear further away. Draw a picture. 3) 26 degrees 4) N = 1.31 5) 51.9 degrees 6) 42.8 degrees 7) (a) 40.8 degrees (b) 60.6 degrees.</p>