2-1 Parabolic Dish Activity Purpose: This activity will introduce the students to parabolic dishes as a means of collecting and reflecting energy to a focal point (focus). Materials: 1. 2. 3. 4. 5. 6. umbrella(s) roll of mylar (or aluminum foil) infrared heat probe non conductive material (sheet of stiff plastic) tape scissors Activity: 1. 2. 3. 4. Students will work in small groups of 2 or3. Each group will take an umbrella and cover the inside with mylar. Use clear tape to secure the mylar. The mylar covered umbrella will be used to reflect light to a focal point along the pole of the umbrella. 5. Tape ½ x 1 inch pieces of plastic along the pole spaced about a ½ inch apart. 6. Students will use a infrared temperature probe to determine where along the pole the focal point is found. Analysis and Conclusion Questions: 1. Where was the focal point found along the pole of your umbrella? 2. How did you determine that this was the focal point? 3. Why is the receiver placed at the focal point? 2-1 4. What problems would you have if the receiver were placed a few centimeters from the focal point? 5. Extra Credit: Write the general equation for a parabola. What is the focus of the parabola?