Introduction to sound and light waves. Discuss waves being formed by vibrations. Show that sound requires a medium which light does not require. Define vibrations. Demonstrate using a pendulum how the length of the pendulum affects the period but not the mass of the pendulum. Define period. Discuss units used in defining frequency, (vibrations/sec and cycles/sed) Relate them both to Hertz units. Eliitc that the period is equivalent to 1/frequency of the wave