LECTURE HANDOUT: REFRACTION OF LIGHT I. Review Each of the diagrams at right shows a ray incident on a boundary between two media. Continue each of the rays into the second medium. Using a dashed line, also draw the path that the wave would have taken if it had continued without "bending." Does the ray representing a wave "bend" toward or away from the normal when: the wave speed is smaller in the second medium? ⚫the wave speed is larger in the second medium? Faster medium Slower medium Slower medium Faster medium II. Qualitative applications of refraction A. Place a coin at the bottom of an empty can or cup. Look into the cup at the coin while your partner slowly moves the can away from you until you no longer see the coin. Now, keep your head steady while your partner gently pours water into the cup. 1. Describe your observations. Switch roles with your partner so that you each have a turn. Shown below are cross-sectional diagrams of the cup for when it was empty and when it was full. 2. On the first diagram, a ray has been drawn from the edge of the coin to the rim of the cup. Indicate the location of your eye on that diagram so that it illustrates why you were unable to see the coin when the cup was empty. 3. On the second diagram, draw a ray that originates from the coin in order to show how you were able to see the coin after the water was added. (Your eye location should be the same as before.) On the basis of your diagram, in which medium does light travel more quickly: in water or in air? Cup empty Coin Water From Tutorials in Introductory Physics, Department of Physics, University of Washington, Fall 2001. B. Suppose you are a contestant on "Survivor XXVII," preparing to spear a fish for dinner. You see a fish that appears to be at the location shown. You have one shot; if you miss, the fish will dart away. In order to throw the spear where the fish is actually located, which of the labeled points (A, B, or C) best represents where you should aim? Draw a ray diagram to support your answer. A B с ھے۔ Apparent location of fish C. A piece of cardboard 4.0 cm tall is placed between a very small light bulb and a screen. The cardboard is 14 cm from the bulb and 20 cm from the screen, as shown in the diagram below. 1. Suppose that a block of plastic were placed between the cardboard and the screen, as shown below right ("plastic > Mair). Would inserting the plastic cause the height of the shadow on the screen to increase, decrease or stay the same? Support your answer by drawing rays on both of the diagrams provided. side view diagram (not to scale) very small bulb cardboard 14 cm- 4.0 cm 20 cm- 77777 very small bulb cardboard plastic screen screen 2. Determine the height of the shadow (in cm) seen on the screen (i) without the plastic block present, and (ii) with the plastic block present. Use plastic 1.3 for the index of refraction of the plastic block. Show all work. From Tutorials in Introductory Physics, Department of Physics, University of Washington, Fall 2001.