ACTIVITY #14: Electromagnetic Waves and the Transfer of Energy The wind starts to pick up and the air temperature begins to drop. In the distance you see a large storm cloud approaching fast. As you take shelter indoors, you see a flash of lighting and then hear the crash of thunder. The storm is now here! As you watch the storm with your sister, she tells you to count the seconds between the lightning flash and the thunder. If the time increases, it means that the storm is moving away. After counting several lighting/thunder combinations you relax as you realize that the storm is moving away from the area. Why does a sudden change in air temperature accompany a storm? Why is there a delay between the lightning and thunder? Do lightning and thunder occur at the same time? Is lightning energy? … is thunder energy?

GOALS: In this lab activity, you will … Learn about electromagnetic waves, how they are grouped, and how each group of waves is important in our lives. Learn which characteristics of a wave determine how much energy it carries. Learn about visible light waves and how the energy carried by these waves enables us to see. Learn what can happen when a wave strikes a substance, and how it delivers energy to a substance. Learn that the different groups of waves behave differently when they strike substances. These differences can have an important impact on the substances.

Activity Overview: A synopsis of this lesson is as follows…   In this activity we continue to investigate the properties of waves by looking at electromagnetic waves. This activity opens by comparing electromagnetic waves and mechanical waves. We then look at the specific characteristics of waves that enable us to judge how much energy the waves carry. Electromagnetic waves are formally introduced, and divided into seven groups. The role that visible light waves play in our ability to see is discussed in the context of the energy these waves carry. We then look at how our eyes receive and detect colors, and discuss the concept of ‘white light’. The final part of the activity addresses what happens to the energy carried by a wave when it strikes a substance. In this part we investigate reflection, refraction, transmission and the absorption of visible light, infrared waves and ultraviolet waves.

Scientific Content - Electromagnetic waves are disturbances in the electric fields and magnetic fields that are created by moving charged particles. They carry electrical energy and magnetic energy. This energy is transported without the need for vibrating particles, so electromagnetic waves can be transported through the vacuum of space. The amplitude and frequency of a wave together determine how much energy is carried by the wave. Visible light allows us to see objects when light leaving these objects enters our eyes and enables us to see. When waves strike a surface, some of the waves reflect off of the surface and the rest enter the material. The waves that reflect off of the surface allow us to see the object and the color. If waves are absorbed, their energy is transformed into a different form within the material, usually heat.